org.jetbrains.kotlin.backend.jvm.lower.MappedEnumWhenLowering.kt Maven / Gradle / Ivy
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/*
* Copyright 2010-2019 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.
*/
package org.jetbrains.kotlin.backend.jvm.lower
import org.jetbrains.kotlin.backend.common.lower.EnumWhenLowering
import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
import org.jetbrains.kotlin.backend.common.lower.irCatch
import org.jetbrains.kotlin.backend.common.phaser.PhaseDescription
import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
import org.jetbrains.kotlin.backend.jvm.JvmLoweredDeclarationOrigin
import org.jetbrains.kotlin.backend.jvm.ir.findEnumValuesFunction
import org.jetbrains.kotlin.backend.jvm.ir.isInPublicInlineScope
import org.jetbrains.kotlin.backend.jvm.isPublicAbi
import org.jetbrains.kotlin.ir.IrStatement
import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
import org.jetbrains.kotlin.ir.builders.*
import org.jetbrains.kotlin.ir.builders.declarations.addField
import org.jetbrains.kotlin.ir.builders.declarations.buildClass
import org.jetbrains.kotlin.ir.declarations.IrClass
import org.jetbrains.kotlin.ir.declarations.IrDeclaration
import org.jetbrains.kotlin.ir.declarations.IrEnumEntry
import org.jetbrains.kotlin.ir.declarations.IrField
import org.jetbrains.kotlin.ir.expressions.IrExpression
import org.jetbrains.kotlin.ir.expressions.impl.IrGetEnumValueImpl
import org.jetbrains.kotlin.ir.types.defaultType
import org.jetbrains.kotlin.ir.types.getClass
import org.jetbrains.kotlin.ir.util.*
import org.jetbrains.kotlin.name.Name
import org.jetbrains.kotlin.util.OperatorNameConventions
// A version of EnumWhenLowering that is more friendly to incremental compilation. For example,
// suppose the code initially looks like this:
//
// // 1.kt
// enum E { X }
//
// // 2.kt
// fun f(e: E) = when (e) { E.X -> 1 }
//
// EnumWhenLowering would transform 2.kt into this:
//
// fun f(e: E) = when (e.ordinal()) { 0 -> 1 }
//
// While this lowering would generate (approximately) this instead:
//
// fun f(e: E) = when (WhenMappings.$EnumSwitchMapping$0[e.ordinal()]) { 1 -> 1 }
//
// object WhenMappings {
// // Note the runtime call to ordinal(): 0 is not hardcoded.
// val $EnumSwitchMapping$0 = IntArray(E.values().size).also { it[E.X.ordinal()] = 1 }
// }
//
// The latter would not need to be recompiled if new entries were added before `X`
// at the negligible cost of an additional initializer per run + one array read per call.
//
@PhaseDescription(
name = "EnumWhenLowering",
description = "Replace `when` subjects of enum types with their ordinals"
)
internal class MappedEnumWhenLowering(override val context: JvmBackendContext) : EnumWhenLowering(context) {
private val intArray = context.irBuiltIns.primitiveArrayForType.getValue(context.irBuiltIns.intType)
private val intArrayConstructor = intArray.constructors.single { it.owner.valueParameters.size == 1 }
private val intArrayGet = intArray.functions.single { it.owner.name == OperatorNameConventions.GET }
private val intArraySet = intArray.functions.single { it.owner.name == OperatorNameConventions.SET }
private val refArraySize = context.irBuiltIns.arrayClass.owner.properties.single { it.name.toString() == "size" }.getter!!
// To avoid visibility-related issues, classes containing the mappings are direct children
// of the classes in which they are used. This field tracks which container is the innermost one.
private var state: EnumMappingState? = null
private class EnumMappingClass(
val field: IrField,
val ordinals: MutableMap = mutableMapOf(),
var isPublicAbi: Boolean = false,
)
private inner class EnumMappingState {
val mappings = mutableMapOf()
val mappingsClass by lazy {
context.irFactory.buildClass {
name = Name.identifier("WhenMappings")
origin = JvmLoweredDeclarationOrigin.ENUM_MAPPINGS_FOR_WHEN
}.apply {
createImplicitParameterDeclarationWithWrappedDescriptor()
}
}
fun getMappingForClass(enumClass: IrClass): EnumMappingClass =
mappings.getOrPut(enumClass) {
EnumMappingClass(mappingsClass.addField {
name = Name.identifier("\$EnumSwitchMapping\$${mappings.size}")
type = intArray.defaultType
origin = JvmLoweredDeclarationOrigin.ENUM_MAPPINGS_FOR_WHEN
isFinal = true
isStatic = true
})
}
val isPublicAbi: Boolean
get() = mappings.values.any { it.isPublicAbi }
}
override fun mapConstEnumEntry(entry: IrEnumEntry): Int {
val mapping = state!!.getMappingForClass(entry.parentAsClass).ordinals
// Index 0 (default value for integers) is reserved for unknown ordinals.
return mapping.getOrPut(entry) { mapping.size + 1 }
}
override fun mapRuntimeEnumEntry(builder: IrBuilderWithScope, subject: IrExpression): IrExpression =
builder.irCall(intArrayGet).apply {
val mapping = state!!.getMappingForClass(subject.type.getClass()!!)
mapping.isPublicAbi = mapping.isPublicAbi ||
(builder.scope.scopeOwnerSymbol.owner as? IrDeclaration)?.isInPublicInlineScope == true
dispatchReceiver = builder.irGetField(null, mapping.field)
putValueArgument(0, super.mapRuntimeEnumEntry(builder, subject))
}
override fun visitClassNew(declaration: IrClass): IrStatement {
val oldState = state
val mappingState = EnumMappingState()
state = mappingState
super.visitClassNew(declaration)
for ((enum, mapping) in mappingState.mappings) {
val enumValues = enum.findEnumValuesFunction(context)
val builder = context.createIrBuilder(mapping.field.symbol)
mapping.field.initializer = builder.irExprBody(builder.irBlock {
val enumSize = irCall(refArraySize).apply { dispatchReceiver = irCall(enumValues) }
val result = irTemporary(irCall(intArrayConstructor).apply { putValueArgument(0, enumSize) })
for ((entry, index) in mapping.ordinals) {
val runtimeEntry = IrGetEnumValueImpl(UNDEFINED_OFFSET, UNDEFINED_OFFSET, enum.defaultType, entry.symbol)
val writeToMapping = irCall(intArraySet).apply {
dispatchReceiver = irGet(result)
putValueArgument(0, super.mapRuntimeEnumEntry(builder, runtimeEntry)) // .ordinal()
putValueArgument(1, irInt(index))
}
val noSuchFieldVariable = scope.createTemporaryVariableDeclaration(
this@MappedEnumWhenLowering.context.ir.symbols.noSuchFieldErrorType,
startOffset = UNDEFINED_OFFSET,
endOffset = UNDEFINED_OFFSET
)
+irTry(
// Ignore NoSuchFieldError in case this module is running with a version of the dependency
// that is missing some of the enum's fields; the corresponding branches are then effectively
// unreachable code (KT-38637)
context.irBuiltIns.unitType, writeToMapping, listOf(irCatch(noSuchFieldVariable, irUnit())),
finallyExpression = null
)
}
+irGet(result)
})
}
if (mappingState.mappings.isNotEmpty()) {
declaration.declarations += mappingState.mappingsClass.apply {
parent = declaration
if (mappingState.isPublicAbi) {
this.isPublicAbi = true
}
}
}
state = oldState
return declaration
}
}