JVM IR: replace unnecessary property accessor calls with field access

Split the ConstAndJvmFieldPropertiesLowering into two: ConstLowering
which replaces const vals with their values, and
PropertiesToFieldsLowering which removes unnecessary property accessors
(such as for JvmField or private properties with default accessors) and
replaces calls to those accessors with field access

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmLower.kt

@@ -16,7 +16,7 @@
 
 package org.jetbrains.kotlin.backend.jvm
 
-import org.jetbrains.kotlin.backend.common.*
+import org.jetbrains.kotlin.backend.common.CommonBackendContext
 import org.jetbrains.kotlin.backend.common.lower.*
 import org.jetbrains.kotlin.backend.common.phaser.*
 import org.jetbrains.kotlin.backend.jvm.lower.*
@@ -46,7 +46,8 @@ internal val jvmPhases = namedIrFilePhase(
             jvmLateinitPhase then
 
             moveCompanionObjectFieldsPhase then
-            constAndJvmFieldPropertiesPhase then
+            constPhase then
+            propertiesToFieldsPhase then
             propertiesPhase then
             annotationPhase then
 

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/ConstLowering.kt

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.backend.jvm.lower
+
+import org.jetbrains.kotlin.backend.common.CommonBackendContext
+import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
+import org.jetbrains.kotlin.ir.expressions.IrCall
+import org.jetbrains.kotlin.ir.expressions.IrConst
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
+
+internal val constPhase = makeIrFilePhase(
+    ::ConstLowering,
+    name = "Const",
+    description = "Substitute calls to const properties with constant values"
+)
+
+class ConstLowering(val context: CommonBackendContext) : IrElementTransformerVoid(), FileLoweringPass {
+    override fun lower(irFile: IrFile) {
+        irFile.transformChildrenVoid(this)
+    }
+
+    override fun visitCall(expression: IrCall): IrExpression {
+        val irSimpleFunction = (expression.symbol.owner as? IrSimpleFunction) ?: return super.visitCall(expression)
+        val irProperty = irSimpleFunction.correspondingProperty ?: return super.visitCall(expression)
+
+        if (irProperty.isConst) {
+            (irProperty.backingField!!.initializer!!.expression as IrConst<*>).let { return it }
+        }
+
+        return super.visitCall(expression)
+    }
+}

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/PropertiesToFieldsLowering.kt

@@ -10,9 +10,14 @@ import org.jetbrains.kotlin.backend.common.FileLoweringPass
 import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
 import org.jetbrains.kotlin.backend.common.lower.irBlock
 import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
+import org.jetbrains.kotlin.descriptors.ClassKind
+import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.declarations.*
-import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.expressions.IrCall
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrFieldAccessExpression
+import org.jetbrains.kotlin.ir.expressions.IrTypeOperator
 import org.jetbrains.kotlin.ir.expressions.impl.*
 import org.jetbrains.kotlin.ir.types.classifierOrFail
 import org.jetbrains.kotlin.ir.util.hasAnnotation
@@ -20,45 +25,54 @@ import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 import org.jetbrains.kotlin.load.java.JvmAbi.JVM_FIELD_ANNOTATION_FQ_NAME
 
-internal val constAndJvmFieldPropertiesPhase = makeIrFilePhase(
-    ::ConstAndJvmFieldPropertiesLowering,
-    name = "ConstAndJvmFieldProperties",
-    description = "Substitute calls to const and Jvm>Field properties with const/field access"
+internal val propertiesToFieldsPhase = makeIrFilePhase(
+    ::PropertiesToFieldsLowering,
+    name = "PropertiesToFields",
+    description = "Replace calls to default property accessors with field access and remove those accessors"
 )
 
-private class ConstAndJvmFieldPropertiesLowering(val context: CommonBackendContext) : IrElementTransformerVoid(), FileLoweringPass {
+class PropertiesToFieldsLowering(val context: CommonBackendContext) : IrElementTransformerVoid(), FileLoweringPass {
     override fun lower(irFile: IrFile) {
         irFile.transformChildrenVoid(this)
     }
 
     override fun visitProperty(declaration: IrProperty): IrStatement {
-        if (declaration.isConst || declaration.backingField?.hasAnnotation(JVM_FIELD_ANNOTATION_FQ_NAME) == true) {
-            /*Safe or need copy?*/
+        if (declaration.isConst || shouldSubstituteAccessorWithField(declaration, declaration.getter)) {
             declaration.getter = null
+        }
+        if (declaration.isConst || shouldSubstituteAccessorWithField(declaration, declaration.setter)) {
             declaration.setter = null
         }
         return super.visitProperty(declaration)
     }
 
     override fun visitCall(expression: IrCall): IrExpression {
-        val irSimpleFunction = (expression.symbol.owner as? IrSimpleFunction) ?: return super.visitCall(expression)
-        val irProperty = irSimpleFunction.correspondingProperty ?: return super.visitCall(expression)
+        val simpleFunction = (expression.symbol.owner as? IrSimpleFunction) ?: return super.visitCall(expression)
+        val property = simpleFunction.correspondingProperty ?: return super.visitCall(expression)
 
-        if (irProperty.isConst) {
-            (irProperty.backingField!!.initializer!!.expression as IrConst<*>).let { return it }
-        }
-
-        if (irProperty.backingField?.hasAnnotation(JVM_FIELD_ANNOTATION_FQ_NAME) == true) {
-            return if (expression is IrGetterCallImpl) {
-                substituteGetter(irProperty, expression)
-            } else {
-                assert(expression is IrSetterCallImpl)
-                substituteSetter(irProperty, expression)
+        if (shouldSubstituteAccessorWithField(property, simpleFunction)) {
+            when (expression) {
+                is IrGetterCallImpl -> return substituteGetter(property, expression)
+                is IrSetterCallImpl -> return substituteSetter(property, expression)
             }
         }
+
         return super.visitCall(expression)
     }
 
+    private fun shouldSubstituteAccessorWithField(property: IrProperty, accessor: IrSimpleFunction?): Boolean {
+        if (accessor == null) return false
+
+        // In contrast to the old backend, we do generate getters for lateinit properties, which fixes KT-28331
+        if (property.isLateinit) return false
+
+        if ((property.parent as? IrClass)?.kind == ClassKind.ANNOTATION_CLASS) return false
+
+        if (property.backingField?.hasAnnotation(JVM_FIELD_ANNOTATION_FQ_NAME) == true) return true
+
+        return accessor.origin == IrDeclarationOrigin.DEFAULT_PROPERTY_ACCESSOR && Visibilities.isPrivate(accessor.visibility)
+    }
+
     private fun substituteSetter(irProperty: IrProperty, expression: IrCall): IrExpression {
         val backingField = irProperty.backingField!!
         val receiver = expression.dispatchReceiver?.transform(this, null)

compiler/testData/codegen/box/multifileClasses/kt16077.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 // TARGET_BACKEND: JVM
 // WITH_RUNTIME
 

compiler/testData/codegen/bytecodeText/companion/kt14258_1.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 // Checks that methods 'access$getMy$p', 'access$getMy$cp' and 'getMy' are not generated and
 // that backed field 'my' is directly used through a 'getstatic'
 

compiler/testData/codegen/bytecodeText/redundantInitializer.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 package a
 
 class A {

compiler/testData/codegen/bytecodeText/redundantInitializerNumber.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 package a
 
 class A {