org.jetbrains.kotlin.backend.jvm.lower.JvmStringConcatenationLowering.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.FileLoweringPass
import org.jetbrains.kotlin.backend.common.IrElementTransformerVoidWithContext
import org.jetbrains.kotlin.backend.common.lower.FlattenStringConcatenationLowering
import org.jetbrains.kotlin.backend.common.lower.loops.ForLoopsLowering
import org.jetbrains.kotlin.backend.common.phaser.PhaseDescription
import org.jetbrains.kotlin.backend.jvm.InlineClassAbi
import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
import org.jetbrains.kotlin.backend.jvm.ir.JvmIrBuilder
import org.jetbrains.kotlin.backend.jvm.ir.createJvmIrBuilder
import org.jetbrains.kotlin.backend.jvm.ir.representativeUpperBound
import org.jetbrains.kotlin.ir.builders.*
import org.jetbrains.kotlin.ir.declarations.*
import org.jetbrains.kotlin.ir.expressions.*
import org.jetbrains.kotlin.ir.expressions.impl.IrStringConcatenationImpl
import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
import org.jetbrains.kotlin.ir.types.*
import org.jetbrains.kotlin.ir.util.constructors
import org.jetbrains.kotlin.ir.util.functions
import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
private val IrClass.toStringFunction: IrSimpleFunction
get() = functions.single {
with(FlattenStringConcatenationLowering) { it.isToString }
}
private fun JvmIrBuilder.callToString(expression: IrExpression): IrExpression {
val argument = normalizeArgument(expression)
val argumentType = if (argument.type.isPrimitiveType()) argument.type else context.irBuiltIns.anyNType
return irCall(backendContext.ir.symbols.typeToStringValueOfFunction(argumentType)).apply {
putValueArgument(0, argument)
}
}
private fun JvmIrBuilder.normalizeArgument(expression: IrExpression): IrExpression {
val type = expression.type
if (type.isByte() || type.isShort()) {
// There is no special append or valueOf function for byte and short on the JVM.
return irImplicitCast(expression, context.irBuiltIns.intType)
}
if (expression is IrConst && expression.kind == IrConstKind.String && (expression.value as String).length == 1) {
// PSI2IR generates const Strings for 1-length literals in string templates (e.g., the space between x and y in "$x $y").
// We want to use the more efficient `append(Char)` function in such cases. This mirrors the behavior of the non-IR backend.
//
// In addition, this also means `append(Char)` will be used for the space in the following case: `x + " " + y`.
// The non-IR backend will still use `append(String)` in this case.
// NB KT-50091 shows an outlier where this might be actually less efficient, but in general we prefer `Char`.
return irChar((expression.value as String)[0])
}
val typeParameterSymbol = type.classifierOrNull as? IrTypeParameterSymbol
if (typeParameterSymbol != null) {
// Upcast type parameter to upper bound with specialized 'append' function
val upperBound = typeParameterSymbol.owner.representativeUpperBound
if (upperBound.classifierOrNull == context.irBuiltIns.stringClass) {
// T <: String || T <: String? =>
// upcast to 'String?'
return irImplicitCast(expression, context.irBuiltIns.stringType.makeNullable())
}
if (!type.isNullable()) {
if (upperBound.isByte() || upperBound.isShort()) {
// Expression type is not null,
// T <: Byte || T <: Short =>
// upcast to Int
return irImplicitCast(expression, context.irBuiltIns.intType)
} else if (upperBound.isPrimitiveType()) {
// Expression type is not null,
// T <: P, P is primitive type (other than 'Byte' or 'Short') =>
// upcast to P
return irImplicitCast(expression, upperBound)
}
}
}
return expression
}
private fun JvmIrBuilder.lowerInlineClassArgument(expression: IrExpression): IrExpression? {
if (InlineClassAbi.unboxType(expression.type) == null)
return null
val toStringFunction = expression.type.classOrNull?.owner?.toStringFunction
?.let { (it as? IrAttributeContainer)?.attributeOwnerId as? IrFunction ?: it }
?: return null
val toStringReplacement = backendContext.inlineClassReplacements.getReplacementFunction(toStringFunction)
?: return null
// `C?` can only be unboxed if it wraps a reference type `T!!`, in which case the unboxed type
// is `T?`. We can't pass that to `C.toString-impl` without checking for `null`.
return if (expression.type.isNullable())
irLetS(expression) {
irIfNull(context.irBuiltIns.stringType, irGet(it.owner), irString(null.toString()), irCall(toStringReplacement).apply {
putValueArgument(0, irGet(it.owner))
})
}
else
irCall(toStringReplacement).apply { putValueArgument(0, expression) }
}
private fun IrExpression.unwrapImplicitNotNull() =
if (this is IrTypeOperatorCall && operator == IrTypeOperator.IMPLICIT_NOTNULL)
argument
else
this
private const val MAX_STRING_CONCAT_DEPTH = 23
/**
* This lowering pass replaces [IrStringConcatenation]s with StringBuilder appends.
*
* This pass is based on [StringConcatenationLowering] in backend.common. The main difference
* is that this pass also handles JVM specific optimizations, such as calling stringPlus
* for two arguments, and properly handles inline classes.
*/
@PhaseDescription(
name = "StringConcatenation",
description = "Replace IrStringConcatenation with string builders",
// FlattenStringConcatenationLowering consolidates string concatenation expressions.
// ForLoopsLowering may produce IrStringConcatenations.
prerequisite = [FlattenStringConcatenationLowering::class, ForLoopsLowering::class]
)
internal class JvmStringConcatenationLowering(val context: JvmBackendContext) : FileLoweringPass, IrElementTransformerVoidWithContext() {
override fun lower(irFile: IrFile) = irFile.transformChildrenVoid()
private val stringBuilder = context.ir.symbols.stringBuilder.owner
private val constructor = stringBuilder.constructors.single {
it.valueParameters.isEmpty()
}
private val toStringFunction = stringBuilder.toStringFunction
private val appendAnyNFunction =
findStringBuilderAppendFunctionWithParameter { it.type.isNullableAny() }!!
private val appendStringNFunction =
findStringBuilderAppendFunctionWithParameter { it.type.classOrNull == context.irBuiltIns.stringClass }!!
private val appendFunctionsByParameterType: Map =
stringBuilder.functions
.filter { it.isAppendFunction() }
.associateBy { it.valueParameters[0].type }
private inline fun findStringBuilderAppendFunctionWithParameter(predicate: (IrValueParameter) -> Boolean) =
stringBuilder.functions.find {
it.isAppendFunction() && predicate(it.valueParameters[0])
}
private fun IrSimpleFunction.isAppendFunction() =
name.asString() == "append" && valueParameters.size == 1
private fun typeToAppendFunction(type: IrType): IrSimpleFunction {
appendFunctionsByParameterType[type]?.let { return it }
if (type.classOrNull == context.irBuiltIns.stringClass)
return appendStringNFunction
return appendAnyNFunction
}
override fun visitStringConcatenation(expression: IrStringConcatenation): IrExpression {
expression.transformChildrenVoid(this)
return context.createJvmIrBuilder(currentScope!!, expression).run {
// When `String.plus(Any?)` is invoked with receiver of platform type String or String with enhanced nullability, this could
// fail a nullability check (NullPointerException) on the receiver. However, the non-IR backend currently does NOT insert this
// check (see KT-36625, pending language design decision). To maintain compatibility with the non-IR backend, we remove
// IMPLICIT_NOTNULL casts from all arguments (nullability checks are generated in JvmArgumentNullabilityAssertionsLowering).
val arguments = expression.arguments
when {
arguments.isEmpty() ->
irString("")
arguments.size == 1 ->
lowerInlineClassArgument(arguments[0]) ?: callToString(arguments[0].unwrapImplicitNotNull())
this@JvmStringConcatenationLowering.context.config.runtimeStringConcat.isDynamic ->
lowerConcatenationDynamic(expression, arguments)
else ->
lowerConcatenationPlain(arguments)
}
}
}
private fun JvmIrBuilder.lowerConcatenationPlain(arguments: MutableList): IrExpression =
if (arguments.size < MAX_STRING_CONCAT_DEPTH) {
irCall(toStringFunction).apply {
dispatchReceiver = appendWindow(arguments, irCall(constructor))
}
} else {
// arguments.size >= MAX_STRING_CONCAT_DEPTH. Prevent SOE in ExpressionCodegen.
// Generates:
// {
// val tmp = StringBuilder()
// tmp.append(a0).append(a1) /* ... */ .append(a21).append(a22)
// /* ... repeat for each possibly partial MAX_STRING_CONCAT_DEPTH-element window ... */
// tmp.toString()
// }
irBlock {
val tmpStringBuilder = irTemporary(irCall(constructor))
val argsWindowed =
arguments.windowed(
size = MAX_STRING_CONCAT_DEPTH,
step = MAX_STRING_CONCAT_DEPTH,
partialWindows = true
)
for (argsWindow in argsWindowed) {
+appendWindow(argsWindow, irGet(tmpStringBuilder))
}
+irCall(toStringFunction).apply { dispatchReceiver = irGet(tmpStringBuilder) }
}
}
private fun JvmIrBuilder.lowerConcatenationDynamic(
expression: IrStringConcatenation, arguments: MutableList,
): IrExpression =
IrStringConcatenationImpl(
expression.startOffset,
expression.endOffset,
expression.type,
arguments.map { argument ->
lowerInlineClassArgument(argument) ?: argument.unwrapImplicitNotNull()
})
private fun JvmIrBuilder.appendWindow(arguments: List, stringBuilder0: IrExpression): IrExpression {
return arguments.fold(stringBuilder0) { stringBuilder, arg ->
val argument = normalizeArgument(arg)
val appendFunction = typeToAppendFunction(argument.type)
irCall(appendFunction).apply {
dispatchReceiver = stringBuilder
// Unwrapping IMPLICIT_NOTNULL is necessary for ALL arguments. There could be a call to `String.plus(Any?)`
// anywhere in the flattened IrStringConcatenation expression, e.g., `"foo" + (Java.platformString() + 123)`.
putValueArgument(0, lowerInlineClassArgument(argument) ?: argument.unwrapImplicitNotNull())
}
}
}
}