Added external serializers in serialization plugin for IR backend

- added fallback support of external serializers in IR
- implemented calculations of properties default values in IR
- swapped check of shouldEncodeElementDefault and comparing the property with default value in IR. Now default value calculated only of shouldEncodeElementDefault returns false

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/common/SerializableCodegen.kt

@@ -5,14 +5,11 @@
 
 package org.jetbrains.kotlinx.serialization.compiler.backend.common
 
-import org.jetbrains.kotlin.config.ApiVersion
 import org.jetbrains.kotlin.descriptors.ClassConstructorDescriptor
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.resolve.BindingContext
-import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.resolve.descriptorUtil.secondaryConstructors
-import org.jetbrains.kotlinx.serialization.compiler.diagnostic.VersionReader
 import org.jetbrains.kotlinx.serialization.compiler.resolve.*
 
 abstract class SerializableCodegen(
@@ -22,9 +19,6 @@ abstract class SerializableCodegen(
     protected val properties = bindingContext.serializablePropertiesFor(serializableDescriptor)
     protected val staticDescriptor = serializableDescriptor.declaredTypeParameters.isEmpty()
 
-    private val fieldMissingOptimizationVersion = ApiVersion.parse("1.1")!!
-    protected val useFieldMissingOptimization = canUseFieldMissingOptimization()
-
     fun generate() {
         generateSyntheticInternalConstructor()
         generateSyntheticMethods()
@@ -49,40 +43,6 @@ abstract class SerializableCodegen(
         }
     }
 
-    protected fun getGoldenMask(): Int {
-        var goldenMask = 0
-        var requiredBit = 1
-        for (property in properties.serializableProperties) {
-            if (!property.optional) {
-                goldenMask = goldenMask or requiredBit
-            }
-            requiredBit = requiredBit shl 1
-        }
-        return goldenMask
-    }
-
-    protected fun getGoldenMaskList(): List<Int> {
-        val maskSlotCount = properties.serializableProperties.bitMaskSlotCount()
-        val goldenMaskList = MutableList(maskSlotCount) { 0 }
-
-        for (i in properties.serializableProperties.indices) {
-            if (!properties.serializableProperties[i].optional) {
-                val slotNumber = i / 32
-                val bitInSlot = i % 32
-                goldenMaskList[slotNumber] = goldenMaskList[slotNumber] or (1 shl bitInSlot)
-            }
-        }
-        return goldenMaskList
-    }
-
-    private fun canUseFieldMissingOptimization(): Boolean {
-        val implementationVersion = VersionReader.getVersionsForCurrentModuleFromContext(
-            serializableDescriptor.module,
-            bindingContext
-        )?.implementationVersion
-        return if (implementationVersion != null) implementationVersion >= fieldMissingOptimizationVersion else false
-    }
-
     protected abstract fun generateInternalConstructor(constructorDescriptor: ClassConstructorDescriptor)
 
     protected open fun generateWriteSelfMethod(methodDescriptor: FunctionDescriptor) {

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/GeneratorHelpers.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -21,10 +21,12 @@ import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.types.impl.IrSimpleTypeImpl
 import org.jetbrains.kotlin.ir.types.impl.makeTypeProjection
 import org.jetbrains.kotlin.ir.util.*
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.js.resolve.diagnostics.findPsi
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.platform.jvm.isJvm
+import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.descriptorUtil.classId
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.descriptorUtil.isEffectivelyExternal
@@ -34,6 +36,7 @@ import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.typeUtil.isTypeParameter
 import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
 import org.jetbrains.kotlin.types.typeUtil.representativeUpperBound
+import org.jetbrains.kotlin.util.OperatorNameConventions
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.*
 import org.jetbrains.kotlinx.serialization.compiler.backend.jvm.*
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
@@ -42,10 +45,20 @@ import org.jetbrains.kotlinx.serialization.compiler.resolve.*
 interface IrBuilderExtension {
     val compilerContext: SerializationPluginContext
 
+    private val throwMissedFieldExceptionFunc
+        get() = compilerContext.referenceFunctions(SerialEntityNames.SINGLE_MASK_FIELD_MISSING_FUNC_FQ).singleOrNull()
+
+    private val throwMissedFieldExceptionArrayFunc
+        get() = compilerContext.referenceFunctions(SerialEntityNames.ARRAY_MASK_FIELD_MISSING_FUNC_FQ).singleOrNull()
+
     private inline fun <reified T : IrDeclaration> IrClass.searchForDeclaration(descriptor: DeclarationDescriptor): T? {
         return declarations.singleOrNull { it.descriptor == descriptor } as? T
     }
 
+    fun useFieldMissingOptimization(): Boolean {
+        return throwMissedFieldExceptionFunc != null && throwMissedFieldExceptionArrayFunc != null
+    }
+
     fun IrClass.contributeFunction(descriptor: FunctionDescriptor, bodyGen: IrBlockBodyBuilder.(IrFunction) -> Unit) {
         val f: IrSimpleFunction = searchForDeclaration(descriptor) ?: compilerContext.symbolTable.referenceSimpleFunction(descriptor).owner
         // TODO: default parameters
@@ -214,14 +227,62 @@ interface IrBuilderExtension {
     // note: this method should be used only for properties from current module. Fields from other modules are private and inaccessible.
     val SerializableProperty.irField: IrField get() = compilerContext.symbolTable.referenceField(this.descriptor).owner
 
-    fun SerializableProperty.getIrPropertyFrom(thisClass: IrClass): IrProperty {
+    fun IrClass.searchForProperty(descriptor: PropertyDescriptor): IrProperty {
-        val desc = this.descriptor
         // this API is used to reference both current module descriptors and external ones (because serializable class can be in any of them),
         // so we use descriptor api for current module because it is not possible to obtain FQname for e.g. local classes.
-        return thisClass.searchForDeclaration(desc) ?: if (desc.module == compilerContext.moduleDescriptor) {
+        return searchForDeclaration(descriptor) ?: if (descriptor.module == compilerContext.moduleDescriptor) {
-            compilerContext.symbolTable.referenceProperty(desc).owner
+            compilerContext.symbolTable.referenceProperty(descriptor).owner
         } else {
-            compilerContext.referenceProperties(desc.fqNameSafe).single().owner
+            compilerContext.referenceProperties(descriptor.fqNameSafe).single().owner
+        }
+    }
+
+    fun SerializableProperty.getIrPropertyFrom(thisClass: IrClass): IrProperty {
+        return thisClass.searchForProperty(descriptor)
+    }
+
+
+    /*
+      Create a function that creates `get property value expressions` for given corresponded constructor's param
+        (constructor_params) -> get_property_value_expression
+     */
+    fun IrBuilderWithScope.createPropertyByParamReplacer(
+        irClass: IrClass,
+        serialProperties: List<SerializableProperty>,
+        instance: IrValueParameter,
+        bindingContext: BindingContext
+    ): (ValueParameterDescriptor) -> IrExpression? {
+        fun SerializableProperty.irGet(): IrExpression {
+            val ownerType = instance.symbol.owner.type
+            return getProperty(
+                irGet(
+                    type = ownerType,
+                    variable = instance.symbol
+                ), getIrPropertyFrom(irClass)
+            )
+        }
+
+        val serialPropertiesMap = serialProperties.associateBy { it.descriptor }
+
+        val transientPropertiesMap =
+            irClass.declarations.asSequence()
+                .filterIsInstance<IrProperty>()
+                .filter { it.backingField != null }.filter { !serialPropertiesMap.containsKey(it.descriptor) }
+                .associateBy { it.symbol.descriptor }
+
+        return {
+            val propertyDescriptor = bindingContext[BindingContext.VALUE_PARAMETER_AS_PROPERTY, it]
+            if (propertyDescriptor != null) {
+                val value = serialPropertiesMap[propertyDescriptor]
+                value?.irGet() ?: transientPropertiesMap[propertyDescriptor]?.let { prop ->
+                    getProperty(
+                        irGet(instance),
+                        prop
+                    )
+                }
+            } else {
+                null
+            }
         }
     }
 
@@ -257,6 +318,78 @@ interface IrBuilderExtension {
         }
     }
 
+    fun IrBlockBodyBuilder.generateGoldenMaskCheck(
+        seenVars: List<IrValueDeclaration>,
+        properties: SerializableProperties,
+        serialDescriptor: IrExpression
+    ) {
+        val fieldsMissedTest: IrExpression
+        val throwErrorExpr: IrExpression
+
+        val maskSlotCount = seenVars.size
+        if (maskSlotCount == 1) {
+            val goldenMask = properties.goldenMask
+
+
+            throwErrorExpr = irInvoke(
+                null,
+                throwMissedFieldExceptionFunc!!,
+                irGet(seenVars[0]),
+                irInt(goldenMask),
+                serialDescriptor,
+                typeHint = compilerContext.irBuiltIns.unitType
+            )
+
+            fieldsMissedTest = irNotEquals(
+                irInt(goldenMask),
+                irBinOp(
+                    OperatorNameConventions.AND,
+                    irInt(goldenMask),
+                    irGet(seenVars[0])
+                )
+            )
+        } else {
+            val goldenMaskList = properties.goldenMaskList
+
+            var compositeExpression: IrExpression? = null
+            for (i in goldenMaskList.indices) {
+                val singleCheckExpr = irNotEquals(
+                    irInt(goldenMaskList[i]),
+                    irBinOp(
+                        OperatorNameConventions.AND,
+                        irInt(goldenMaskList[i]),
+                        irGet(seenVars[i])
+                    )
+                )
+
+                compositeExpression = if (compositeExpression == null) {
+                    singleCheckExpr
+                } else {
+                    irBinOp(
+                        OperatorNameConventions.OR,
+                        compositeExpression,
+                        singleCheckExpr
+                    )
+                }
+            }
+
+            fieldsMissedTest = compositeExpression!!
+
+            throwErrorExpr = irBlock {
+                +irInvoke(
+                    null,
+                    throwMissedFieldExceptionArrayFunc!!,
+                    createPrimitiveArrayOfExpression(compilerContext.irBuiltIns.intType, goldenMaskList.indices.map { irGet(seenVars[it]) }),
+                    createPrimitiveArrayOfExpression(compilerContext.irBuiltIns.intType, goldenMaskList.map { irInt(it) }),
+                    serialDescriptor,
+                    typeHint = compilerContext.irBuiltIns.unitType
+                )
+            }
+        }
+
+        +irIfThen(compilerContext.irBuiltIns.unitType, fieldsMissedTest, throwErrorExpr)
+    }
+
     fun generateSimplePropertyWithBackingField(
         propertyDescriptor: PropertyDescriptor,
         propertyParent: IrClass,
@@ -485,18 +618,45 @@ interface IrBuilderExtension {
         return defaultsMap + extractDefaultValuesFromConstructor(irClass.getSuperClassNotAny())
     }
 
-    fun buildInitializersRemapping(irClass: IrClass): (IrField) -> IrExpression? {
+    /*
-        val defaultsMap = extractDefaultValuesFromConstructor(irClass)
+    Creates an initializer adapter function that can replace IR expressions of getting constructor parameter value by some other expression.
-        return fun(f: IrField): IrExpression? {
+    Also adapter may replace IR expression of getting `this` value by another expression.
-            val i = f.initializer?.expression ?: return null
+     */
-            val irExpression =
+    fun createInitializerAdapter(
-                if (i is IrGetValueImpl && i.origin == IrStatementOrigin.INITIALIZE_PROPERTY_FROM_PARAMETER) {
+        irClass: IrClass,
-                    // this is a primary constructor property, use corresponding default of value parameter
+        paramGetReplacer: (ValueParameterDescriptor) -> IrExpression?,
-                    defaultsMap.getValue(i.symbol.descriptor as ParameterDescriptor)
+        thisGetReplacer: Pair<IrValueSymbol, () -> IrExpression>? = null
-                } else {
+    ): (IrExpressionBody) -> IrExpression {
-                    i
+        val initializerTransformer = object : IrElementTransformerVoid() {
+            // try to replace `get some value` expression
+            override fun visitGetValue(expression: IrGetValue): IrExpression {
+                val symbol = expression.symbol
+                if (thisGetReplacer != null && thisGetReplacer.first == symbol) {
+                    // replace `get this value` expression
+                    return thisGetReplacer.second()
                 }
-            return irExpression?.deepCopyWithVariables()
+
+                val descriptor = symbol.descriptor
+                if (descriptor is ValueParameterDescriptor) {
+                    // replace `get parameter value` expression
+                    paramGetReplacer(descriptor)?.let { return it }
+                }
+
+                // otherwise leave expression as it is
+                return super.visitGetValue(expression)
+            }
+        }
+        val defaultsMap = extractDefaultValuesFromConstructor(irClass)
+        return fun(initializer: IrExpressionBody): IrExpression {
+            val rawExpression = initializer.expression
+            val expression =
+                if (rawExpression is IrGetValueImpl && rawExpression.origin == IrStatementOrigin.INITIALIZE_PROPERTY_FROM_PARAMETER) {
+                    // this is a primary constructor property, use corresponding default of value parameter
+                    defaultsMap.getValue(rawExpression.symbol.descriptor as ParameterDescriptor)!!
+                } else {
+                    rawExpression
+                }
+            return expression.deepCopyWithVariables().transform(initializerTransformer, null)
         }
     }
 

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/SerializableIrGenerator.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -9,10 +9,12 @@ import org.jetbrains.kotlin.backend.common.deepCopyWithVariables
 import org.jetbrains.kotlin.backend.common.lower.irThrow
 import org.jetbrains.kotlin.codegen.CompilationException
 import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.builders.declarations.addField
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrExpressionBody
 import org.jetbrains.kotlin.ir.expressions.impl.IrDelegatingConstructorCallImpl
 import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
 import org.jetbrains.kotlin.ir.types.*
@@ -23,15 +25,14 @@ import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.util.OperatorNameConventions
+import org.jetbrains.kotlin.utils.getOrPutNullable
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.SerializableCodegen
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.serialName
 import org.jetbrains.kotlinx.serialization.compiler.diagnostic.serializableAnnotationIsUseless
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
 import org.jetbrains.kotlinx.serialization.compiler.resolve.*
-import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames.ARRAY_MASK_FIELD_MISSING_FUNC_FQ
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames.MISSING_FIELD_EXC
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames.SERIAL_DESC_FIELD
-import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames.SINGLE_MASK_FIELD_MISSING_FUNC_FQ
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames.initializedDescriptorFieldName
 
 class SerializableIrGenerator(
@@ -50,11 +51,6 @@ class SerializableIrGenerator(
 
     private val addElementFun = serialDescImplClass.findFunctionSymbol(CallingConventions.addElement)
 
-    val throwMissedFieldExceptionFunc =
-        if (useFieldMissingOptimization) compilerContext.referenceFunctions(SINGLE_MASK_FIELD_MISSING_FUNC_FQ).single() else null
-    val throwMissedFieldExceptionArrayFunc =
-        if (useFieldMissingOptimization) compilerContext.referenceFunctions(ARRAY_MASK_FIELD_MISSING_FUNC_FQ).single() else null
-
     private fun IrClass.hasSerializableAnnotationWithoutArgs(): Boolean {
         val annot = getAnnotation(SerializationAnnotations.serializableAnnotationFqName) ?: return false
 
@@ -69,7 +65,40 @@ class SerializableIrGenerator(
 
     override fun generateInternalConstructor(constructorDescriptor: ClassConstructorDescriptor) =
         irClass.contributeConstructor(constructorDescriptor) { ctor ->
-            val transformFieldInitializer = buildInitializersRemapping(irClass)
+            val thiz = irClass.thisReceiver!!
+            val serializableProperties = properties.serializableProperties
+
+            val serialDescs = serializableProperties.map { it.descriptor }.toSet()
+
+            val propertyByParamReplacer: (ValueParameterDescriptor) -> IrExpression? =
+                createPropertyByParamReplacer(irClass, serializableProperties, thiz, bindingContext)
+
+            val initializerAdapter: (IrExpressionBody) -> IrExpression = createInitializerAdapter(irClass, propertyByParamReplacer)
+
+
+            var current: PropertyDescriptor? = null
+            val statementsAfterSerializableProperty: MutableMap<PropertyDescriptor?, MutableList<IrStatement>> = mutableMapOf()
+            irClass.declarations.asSequence().forEach {
+                when {
+                    // only properties with backing field
+                    it is IrProperty && it.backingField != null -> {
+                        if (it.descriptor in serialDescs) {
+                            current = it.descriptor
+                        } else if (it.backingField?.initializer != null) {
+                            // skip transient lateinit or deferred properties (with null initializer)
+                            val expression = initializerAdapter(it.backingField!!.initializer!!)
+
+                            statementsAfterSerializableProperty.getOrPutNullable(current, { mutableListOf() })
+                                .add(irSetField(irGet(thiz), it.backingField!!, expression))
+                        }
+                    }
+                    it is IrAnonymousInitializer -> {
+                        val statements = it.body.deepCopyWithVariables().statements
+                        statementsAfterSerializableProperty.getOrPutNullable(current, { mutableListOf() })
+                            .addAll(statements)
+                    }
+                }
+            }
 
             // Missing field exception parts
             val exceptionFqn = getSerializationPackageFqn(MISSING_FIELD_EXC)
@@ -77,16 +106,19 @@ class SerializableIrGenerator(
                 .single { it.owner.valueParameters.singleOrNull()?.type?.isString() == true }
             val exceptionType = exceptionCtorRef.owner.returnType
 
-            val serializableProperties = properties.serializableProperties
             val seenVarsOffset = serializableProperties.bitMaskSlotCount()
             val seenVars = (0 until seenVarsOffset).map { ctor.valueParameters[it] }
 
-            val thiz = irClass.thisReceiver!!
+
             val superClass = irClass.getSuperClassOrAny()
             var startPropOffset: Int = 0
 
-            if (useFieldMissingOptimization) {
+
-                generateOptimizedGoldenMaskCheck(seenVars)
+            if (useFieldMissingOptimization() &&
+                // for abstract classes fields MUST BE checked in child classes
+                !serializableDescriptor.isAbstractSerializableClass() && !serializableDescriptor.isSealedSerializableClass()
+            ) {
+                generateGoldenMaskCheck(seenVars, properties, getSerialDescriptorExpr())
             }
             when {
                 superClass.symbol == compilerContext.irBuiltIns.anyClass -> generateAnySuperConstructorCall(toBuilder = this@contributeConstructor)
@@ -96,6 +128,7 @@ class SerializableIrGenerator(
                 else -> generateSuperNonSerializableCall(superClass)
             }
 
+            statementsAfterSerializableProperty[null]?.forEach { +it }
             for (index in startPropOffset until serializableProperties.size) {
                 val prop = serializableProperties[index]
                 val paramRef = ctor.valueParameters[index + seenVarsOffset]
@@ -106,13 +139,14 @@ class SerializableIrGenerator(
 
                 val ifNotSeenExpr: IrExpression = if (prop.optional) {
                     val initializerBody =
-                        requireNotNull(transformFieldInitializer(prop.irField)) { "Optional value without an initializer" } // todo: filter abstract here
+                        requireNotNull(initializerAdapter(prop.irField.initializer!!)) { "Optional value without an initializer" } // todo: filter abstract here
                     irSetField(irGet(thiz), backingFieldToAssign, initializerBody)
                 } else {
                     // property required
-                    if (useFieldMissingOptimization) {
+                    if (useFieldMissingOptimization()) {
                         // field definitely not empty as it's checked before - no need another IF, only assign property from param
                         +assignParamExpr
+                        statementsAfterSerializableProperty[prop.descriptor]?.forEach { +it }
                         continue
                     } else {
                         irThrow(irInvoke(null, exceptionCtorRef, irString(prop.name), typeHint = exceptionType))
@@ -130,97 +164,11 @@ class SerializableIrGenerator(
                     )
 
                 +irIfThenElse(compilerContext.irBuiltIns.unitType, propNotSeenTest, ifNotSeenExpr, assignParamExpr)
-            }
 
-            // remaining initializers of variables
+                statementsAfterSerializableProperty[prop.descriptor]?.forEach { +it }
-            val serialDescs = serializableProperties.map { it.descriptor }.toSet()
-            irClass.declarations.asSequence()
-                .filterIsInstance<IrProperty>()
-                .filter { it.descriptor !in serialDescs }
-                .filter { it.backingField != null }
-                .mapNotNull { prop -> transformFieldInitializer(prop.backingField!!)?.let { prop to it } }
-                .forEach { (prop, expr) -> +irSetField(irGet(thiz), prop.backingField!!, expr) }
-
-            // init blocks
-            irClass.declarations.asSequence()
-                .filterIsInstance<IrAnonymousInitializer>()
-                .forEach { initializer ->
-                    initializer.body.deepCopyWithVariables().statements.forEach { +it }
-                }
-        }
-
-    private fun IrBlockBodyBuilder.generateOptimizedGoldenMaskCheck(seenVars: List<IrValueParameter>) {
-        if (serializableDescriptor.isAbstractSerializableClass() || serializableDescriptor.isSealedSerializableClass()) {
-            // for abstract classes fields MUST BE checked in child classes
-            return
-        }
-
-        val fieldsMissedTest: IrExpression
-        val throwErrorExpr: IrExpression
-
-        val maskSlotCount = seenVars.size
-        if (maskSlotCount == 1) {
-            val goldenMask = getGoldenMask()
-
-            throwErrorExpr = irInvoke(
-                null,
-                throwMissedFieldExceptionFunc!!,
-                irGet(seenVars[0]),
-                irInt(goldenMask),
-                getSerialDescriptorExpr(),
-                typeHint = compilerContext.irBuiltIns.unitType
-            )
-
-            fieldsMissedTest = irNotEquals(
-                irInt(goldenMask),
-                irBinOp(
-                    OperatorNameConventions.AND,
-                    irInt(goldenMask),
-                    irGet(seenVars[0])
-                )
-            )
-        } else {
-            val goldenMaskList = getGoldenMaskList()
-
-            var compositeExpression: IrExpression? = null
-            for (i in goldenMaskList.indices) {
-                val singleCheckExpr = irNotEquals(
-                    irInt(goldenMaskList[i]),
-                    irBinOp(
-                        OperatorNameConventions.AND,
-                        irInt(goldenMaskList[i]),
-                        irGet(seenVars[i])
-                    )
-                )
-
-                compositeExpression = if (compositeExpression == null) {
-                    singleCheckExpr
-                } else {
-                    irBinOp(
-                        OperatorNameConventions.OR,
-                        compositeExpression,
-                        singleCheckExpr
-                    )
-                }
-            }
-
-            fieldsMissedTest = compositeExpression!!
-
-            throwErrorExpr = irBlock {
-                +irInvoke(
-                    null,
-                    throwMissedFieldExceptionArrayFunc!!,
-                    createPrimitiveArrayOfExpression(compilerContext.irBuiltIns.intType, goldenMaskList.indices.map { irGet(seenVars[it]) }),
-                    createPrimitiveArrayOfExpression(compilerContext.irBuiltIns.intType, goldenMaskList.map { irInt(it) }),
-                    getSerialDescriptorExpr(),
-                    typeHint = compilerContext.irBuiltIns.unitType
-                )
             }
         }
 
-        +irIfThen(compilerContext.irBuiltIns.unitType, fieldsMissedTest, throwErrorExpr)
-    }
-
     private fun IrBlockBodyBuilder.getSerialDescriptorExpr(): IrExpression {
         return if (serializableDescriptor.shouldHaveGeneratedSerializer && staticDescriptor) {
             val serializer = serializableDescriptor.classSerializer!!

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/SerializerIrGenerator.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -12,10 +12,8 @@ import org.jetbrains.kotlin.backend.common.lower.irThrow
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.*
-import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
+import org.jetbrains.kotlin.ir.expressions.*
-import org.jetbrains.kotlin.ir.expressions.IrExpression
 import org.jetbrains.kotlin.ir.expressions.impl.*
-import org.jetbrains.kotlin.ir.expressions.mapValueParametersIndexed
 import org.jetbrains.kotlin.ir.symbols.IrConstructorSymbol
 import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
 import org.jetbrains.kotlin.ir.symbols.impl.IrAnonymousInitializerSymbolImpl
@@ -23,13 +21,12 @@ import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.platform.jvm.isJvm
 import org.jetbrains.kotlin.resolve.BindingContext
+import org.jetbrains.kotlin.resolve.calls.components.hasDefaultValue
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.util.OperatorNameConventions
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.SerialTypeInfo
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.SerializerCodegen
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.getSerialTypeInfo
-import org.jetbrains.kotlinx.serialization.compiler.backend.jvm.SerializerCodegenImpl
-import org.jetbrains.kotlinx.serialization.compiler.backend.jvm.SerializerForEnumsCodegen
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationDescriptorSerializerPlugin
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
 import org.jetbrains.kotlinx.serialization.compiler.resolve.*
@@ -243,9 +240,6 @@ open class SerializerIrGenerator(
 
     override fun generateSave(function: FunctionDescriptor) = irClass.contributeFunction(function) { saveFunc ->
 
-        val fieldInitializer: (SerializableProperty) -> IrExpression? =
-            buildInitializersRemapping(serializableIrClass).run { { invoke(it.irField) } }
-
         fun irThis(): IrExpression =
             IrGetValueImpl(startOffset, endOffset, saveFunc.dispatchReceiverParameter!!.symbol)
 
@@ -280,16 +274,22 @@ open class SerializerIrGenerator(
         // Ignore comparing to default values of properties from superclass,
         // because we do not have access to their fields (and initializers), if superclass is in another module.
         // In future, IR analogue of JVM's write$Self should be implemented.
-        val superClass = irClass.getSuperClassOrAny().descriptor
+        val superClass = serializableIrClass.getSuperClassOrAny().descriptor
         val ignoreIndexTo = if (superClass.isInternalSerializable) {
             bindingContext.serializablePropertiesFor(superClass).size
         } else {
             -1
         }
 
+        val propertyByParamReplacer: (ValueParameterDescriptor) -> IrExpression? =
+            createPropertyByParamReplacer(serializableIrClass, serializableProperties, objectToSerialize, bindingContext)
+
+        val thisSymbol = serializableIrClass.thisReceiver!!.symbol
+        val initializerAdapter: (IrExpressionBody) -> IrExpression =
+            createInitializerAdapter(serializableIrClass, propertyByParamReplacer, thisSymbol to { irGet(objectToSerialize) })
 
         //  internal serialization via virtual calls?
-        for ((index, property) in serializableProperties.filter { !it.transient }.withIndex()) {
+        for ((index, property) in serializableProperties.withIndex()) {
             // output.writeXxxElementValue(classDesc, index, value)
             val elementCall = formEncodeDecodePropertyCall(irGet(localOutput), saveFunc.dispatchReceiverParameter!!, property, {innerSerial, sti ->
                 val f =
@@ -314,11 +314,12 @@ open class SerializerIrGenerator(
                 +elementCall
             } else {
                 // emit check:
-                // if (obj.prop != DEFAULT_VALUE || output.shouldEncodeElementDefault(this.descriptor, i))
+                // if ( if (output.shouldEncodeElementDefault(this.descriptor, i)) true else {obj.prop != DEFAULT_VALUE} ) {
                 //    output.encodeIntElement(this.descriptor, i, obj.prop)
+                // block {obj.prop != DEFAULT_VALUE} may contain several statements
                 val shouldEncodeFunc = kOutputClass.referenceMethod(CallingConventions.shouldEncodeDefault)
-                val partA = irNotEquals(property.irGet(), fieldInitializer(property)!!)
+                val partA = irInvoke(irGet(localOutput), shouldEncodeFunc, irGet(localSerialDesc), irInt(index))
-                val partB = irInvoke(irGet(localOutput), shouldEncodeFunc, irGet(localSerialDesc), irInt(index))
+                val partB = irNotEquals(property.irGet(), initializerAdapter(property.irField.initializer!!))
                 // Ir infrastructure does not have dedicated symbol for ||, so
                 //  `a || b == if (a) true else b`, see org.jetbrains.kotlin.ir.builders.PrimitivesKt.oror
                 val condition = irIfThenElse(compilerContext.irBuiltIns.booleanType, partA, irTrue(), partB)
@@ -354,8 +355,8 @@ open class SerializerIrGenerator(
     }
 
     // returns null: Any? for boxed types and 0: <number type> for primitives
-    private fun IrBuilderWithScope.defaultValueAndType(prop: SerializableProperty): Pair<IrExpression, IrType> {
+    private fun IrBuilderWithScope.defaultValueAndType(descriptor: PropertyDescriptor): Pair<IrExpression, IrType> {
-        val kType = prop.descriptor.returnType!!
+        val kType = descriptor.returnType!!
         val T = kType.toIrType()
         val defaultPrimitive: IrExpression? = when {
             T.isInt() -> IrConstImpl.int(startOffset, endOffset, T, 0)
@@ -397,12 +398,26 @@ open class SerializerIrGenerator(
         // calculating bit mask vars
         val blocksCnt = serializableProperties.bitMaskSlotCount()
 
+        val serialPropertiesIndexes = serializableProperties
+            .mapIndexed { i, property -> property to i }
+            .associate { (p, i) -> p.descriptor to i }
+
+        val transients = serializableIrClass.declarations.asSequence()
+            .filterIsInstance<IrProperty>()
+            .filter { !serialPropertiesIndexes.containsKey(it.descriptor) }
+            .filter { it.backingField != null }
+
         // var bitMask0 = 0, bitMask1 = 0...
         val bitMasks = (0 until blocksCnt).map { irTemporary(irInt(0), "bitMask$it", isMutable = true) }
         // var local0 = null, local1 = null ...
-        val localProps = serializableProperties.mapIndexed { i, prop ->
+        val serialPropertiesMap = serializableProperties.mapIndexed { i, prop -> i to prop.descriptor }.associate { (i, descriptor) ->
-            val (expr, type) = defaultValueAndType(prop)
+            val (expr, type) = defaultValueAndType(descriptor)
-            irTemporary(expr, "local$i", type, isMutable = true)
+            descriptor to irTemporary(expr, "local$i", type, isMutable = true)
+        }
+        // var transient0 = null, transient0 = null ...
+        val transientsPropertiesMap = transients.mapIndexed { i, prop -> i to prop.descriptor }.associate { (i, descriptor) ->
+            val (expr, type) = defaultValueAndType(descriptor)
+            descriptor to irTemporary(expr, "transient$i", type, isMutable = true)
         }
 
         //input = input.beginStructure(...)
@@ -423,7 +438,7 @@ open class SerializerIrGenerator(
                         inputClass.referenceMethod(
                             "${CallingConventions.decode}${sti.elementMethodPrefix}Serializable${CallingConventions.elementPostfix}", {it.valueParameters.size == 4}
                         ) to listOf(
-                            localSerialDesc.get(), irInt(index), innerSerial, localProps[index].get()
+                            localSerialDesc.get(), irInt(index), innerSerial, serialPropertiesMap.getValue(property.descriptor).get()
                         )
                     }, {
                         inputClass.referenceMethod(
@@ -434,7 +449,7 @@ open class SerializerIrGenerator(
                     }, returnTypeHint = property.type.toIrType())
                     // local$i = localInput.decode...(...)
                     +irSet(
-                        localProps[index].symbol,
+                        serialPropertiesMap.getValue(property.descriptor).symbol,
                         decodeFuncToCall
                     )
                     // bitMask[i] |= 1 << x
@@ -491,17 +506,103 @@ open class SerializerIrGenerator(
             irGet(localSerialDesc)
         )
 
-        // todo: set properties in external deserialization
-        var args: List<IrExpression> = localProps.map { it.get() }
         val typeArgs = (loadFunc.returnType as IrSimpleType).arguments.map { (it as IrTypeProjection).type }
-        val ctor: IrConstructorSymbol = if (serializableDescriptor.isInternalSerializable) {
+        if (serializableDescriptor.isInternalSerializable) {
+            var args: List<IrExpression> = serializableProperties.map { serialPropertiesMap.getValue(it.descriptor).get() }
             args = bitMasks.map { irGet(it) } + args + irNull()
-            serializableSyntheticConstructor(serializableIrClass)
+            val ctor: IrConstructorSymbol = serializableSyntheticConstructor(serializableIrClass)
+            +irReturn(irInvoke(null, ctor, typeArgs, args))
         } else {
-            compilerContext.referenceConstructors(serializableDescriptor.fqNameSafe).single { it.owner.isPrimary }
+            // check properties presence
-        }
+            val serialDescIrProperty = irClass.searchForProperty(generatedSerialDescPropertyDescriptor!!)
+            val serialDescriptorExpr = irGetField(null, serialDescIrProperty.backingField!!)
+            generateGoldenMaskCheck(bitMasks, properties, serialDescriptorExpr)
 
-        +irReturn(irInvoke(null, ctor, typeArgs, args))
+
+            val ctor: IrConstructorSymbol =
+                compilerContext.referenceConstructors(serializableDescriptor.fqNameSafe).single { it.owner.isPrimary }
+            val params = ctor.owner.valueParameters
+
+
+            val variableByParamReplacer: (ValueParameterDescriptor) -> IrExpression? = {
+                val propertyDescriptor = bindingContext[BindingContext.VALUE_PARAMETER_AS_PROPERTY, it]
+                if (propertyDescriptor != null) {
+                    val serializable = serialPropertiesMap[propertyDescriptor]
+                    (serializable ?: transientsPropertiesMap[propertyDescriptor])?.get()
+                } else {
+                    null
+                }
+            }
+            val initializerAdapter: (IrExpressionBody) -> IrExpression =
+                createInitializerAdapter(serializableIrClass, variableByParamReplacer)
+
+            // constructor args:
+            val ctorArgs = params.map { parameter ->
+                val parameterDescriptor = parameter.descriptor as ValueParameterDescriptor
+                val propertyDescriptor = bindingContext[BindingContext.VALUE_PARAMETER_AS_PROPERTY, parameterDescriptor]!!
+                val serialProperty = serialPropertiesMap[propertyDescriptor]
+
+                // null if transient
+                if (serialProperty != null) {
+                    val index = serialPropertiesIndexes.getValue(propertyDescriptor)
+                    if (parameterDescriptor.hasDefaultValue()) {
+                        val propNotSeenTest =
+                            irEquals(
+                                irInt(0),
+                                irBinOp(
+                                    OperatorNameConventions.AND,
+                                    bitMasks[index / 32].get(),
+                                    irInt(1 shl (index % 32))
+                                )
+                            )
+
+                        // if(mask$j && propertyMask == 0) local$i = <initializer>
+                        val defaultValueExp = parameter.defaultValue!!
+                        val expr = initializerAdapter(defaultValueExp)
+                        +irIfThen(propNotSeenTest, irSet(serialProperty.symbol, expr))
+                    }
+                    serialProperty.get()
+                } else {
+                    val transientVar = transientsPropertiesMap.getValue(propertyDescriptor)
+                    if (parameterDescriptor.hasDefaultValue()) {
+                        val defaultValueExp = parameter.defaultValue!!
+                        val expr = initializerAdapter(defaultValueExp)
+                        +irSet(transientVar.symbol, expr)
+                    }
+                    transientVar.get()
+                }
+            }
+
+            val serializerVar = irTemporary(irInvoke(null, ctor, typeArgs, ctorArgs), "serializable")
+            generateSetStandaloneProperties(serializerVar, serialPropertiesMap::getValue, serialPropertiesIndexes::getValue, bitMasks)
+            +irReturn(irGet(serializerVar))
+        }
+    }
+
+    private fun IrBlockBodyBuilder.generateSetStandaloneProperties(
+        serializableVar: IrVariable,
+        propVars: (PropertyDescriptor) -> IrVariable,
+        propIndexes: (PropertyDescriptor) -> Int,
+        bitMasks: List<IrVariable>
+    ) {
+        for (property in properties.serializableStandaloneProperties) {
+            val localPropIndex = propIndexes(property.descriptor)
+            // generate setter call
+            val setter = property.getIrPropertyFrom(serializableIrClass).setter!!
+            val propSeenTest =
+                irNotEquals(
+                    irInt(0),
+                    irBinOp(
+                        OperatorNameConventions.AND,
+                        irGet(bitMasks[localPropIndex / 32]),
+                        irInt(1 shl (localPropIndex % 32))
+                    )
+                )
+
+            val setterInvokeExpr = irSet(setter.returnType, irGet(serializableVar), setter.symbol, irGet(propVars(property.descriptor)))
+
+            +irIfThen(propSeenTest, setterInvokeExpr)
+        }
     }
 
     companion object {

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/jvm/SerializableCodegenImpl.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2017 JetBrains s.r.o.
+ * Copyright 2010-2021 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.
@@ -17,6 +17,7 @@
 package org.jetbrains.kotlinx.serialization.compiler.backend.jvm
 
 import org.jetbrains.kotlin.codegen.*
+import org.jetbrains.kotlin.config.ApiVersion
 import org.jetbrains.kotlin.descriptors.ClassConstructorDescriptor
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor
@@ -30,6 +31,7 @@ import org.jetbrains.kotlin.resolve.descriptorUtil.getSuperClassOrAny
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.resolve.jvm.diagnostics.OtherOrigin
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.*
+import org.jetbrains.kotlinx.serialization.compiler.diagnostic.VersionReader
 import org.jetbrains.kotlinx.serialization.compiler.diagnostic.serializableAnnotationIsUseless
 import org.jetbrains.kotlinx.serialization.compiler.resolve.*
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames.ARRAY_MASK_FIELD_MISSING_FUNC_NAME
@@ -45,6 +47,8 @@ class SerializableCodegenImpl(
 ) : SerializableCodegen(classCodegen.descriptor, classCodegen.bindingContext) {
 
     private val thisAsmType = classCodegen.typeMapper.mapClass(serializableDescriptor)
+    private val fieldMissingOptimizationVersion = ApiVersion.parse("1.1")!!
+    private val useFieldMissingOptimization = canUseFieldMissingOptimization()
 
     companion object {
         fun generateSerializableExtensions(codegen: ImplementationBodyCodegen) {
@@ -289,7 +293,7 @@ class SerializableCodegenImpl(
         val allPresentsLabel = Label()
         val maskSlotCount = properties.serializableProperties.bitMaskSlotCount()
         if (maskSlotCount == 1) {
-            val goldenMask = getGoldenMask()
+            val goldenMask = properties.goldenMask
 
             iconst(goldenMask)
             dup()
@@ -310,7 +314,7 @@ class SerializableCodegenImpl(
         } else {
             val fieldsMissingLabel = Label()
 
-            val goldenMaskList = getGoldenMaskList()
+            val goldenMaskList = properties.goldenMaskList
             goldenMaskList.forEachIndexed { i, goldenMask ->
                 val maskIndex = maskVar + i
                 // if( (goldenMask & seen) != goldenMask )
@@ -404,4 +408,12 @@ class SerializableCodegenImpl(
         this.gen(param.defaultValue, mapType)
         this.v.putfield(thisAsmType.internalName, prop.name.asString(), mapType.descriptor)
     }
+
+    private fun canUseFieldMissingOptimization(): Boolean {
+        val implementationVersion = VersionReader.getVersionsForCurrentModuleFromContext(
+            currentDeclaration.module,
+            bindingContext
+        )?.implementationVersion
+        return if (implementationVersion != null) implementationVersion >= fieldMissingOptimizationVersion else false
+    }
 }

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/SerializableProperties.kt

@@ -88,6 +88,34 @@ class SerializableProperties(private val serializableClass: ClassDescriptor, val
         ?.original?.valueParameters?.any { it.declaresDefaultValue() } ?: false
 }
 
+internal val SerializableProperties.goldenMask: Int
+    get() {
+        var goldenMask = 0
+        var requiredBit = 1
+        for (property in serializableProperties) {
+            if (!property.optional) {
+                goldenMask = goldenMask or requiredBit
+            }
+            requiredBit = requiredBit shl 1
+        }
+        return goldenMask
+    }
+
+internal val SerializableProperties.goldenMaskList: List<Int>
+    get() {
+        val maskSlotCount = serializableProperties.bitMaskSlotCount()
+        val goldenMaskList = MutableList(maskSlotCount) { 0 }
+
+        for (i in serializableProperties.indices) {
+            if (!serializableProperties[i].optional) {
+                val slotNumber = i / 32
+                val bitInSlot = i % 32
+                goldenMaskList[slotNumber] = goldenMaskList[slotNumber] or (1 shl bitInSlot)
+            }
+        }
+        return goldenMaskList
+    }
+
 internal fun List<SerializableProperty>.bitMaskSlotCount() = size / 32 + 1
 internal fun bitMaskSlotAt(propertyIndex: Int) = propertyIndex / 32