JVM IR: Lower IrStringConcatenation

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/FlattenStringConcatenationLowering.kt

@@ -80,42 +80,55 @@ class FlattenStringConcatenationLowering(val context: CommonBackendContext) : Fi
         )
 
         /** @return true if the given expression is a call to [String.plus] */
-        private fun isStringPlusCall(expression: IrCall): Boolean {
+        private val IrCall.isStringPlusCall: Boolean
-            val function = expression.symbol.owner
+            get() {
-            val receiver = expression.dispatchReceiver ?: expression.extensionReceiver
+                val function = symbol.owner
+                val receiver = dispatchReceiver ?: extensionReceiver
 
-            return receiver != null
+                return receiver != null
-                    && receiver.type.isStringClassType()
+                        && receiver.type.isStringClassType()
-                    && function.returnType.isStringClassType()
+                        && function.returnType.isStringClassType()
-                    && function.valueParameters.size == 1
+                        && function.valueParameters.size == 1
-                    && function.name.asString() == "plus"
+                        && function.name.asString() == "plus"
-                    && function.fqNameWhenAvailable?.parent() in PARENT_NAMES
+                        && function.fqNameWhenAvailable?.parent() in PARENT_NAMES
-        }
+            }
+
+        /** @return true if the function is Any.toString or an override of Any.toString */
+        val IrSimpleFunction.isToString: Boolean
+            get() {
+                if (name.asString() != "toString" || valueParameters.size != 0 || !returnType.isString())
+                    return false
+
+                return (dispatchReceiverParameter != null && extensionReceiverParameter == null
+                        && (dispatchReceiverParameter?.type?.isAny() == true || this.overriddenSymbols.isNotEmpty()))
+            }
+
+        /** @return true if the function is Any?.toString */
+        private val IrSimpleFunction.isNullableToString: Boolean
+            get() {
+                if (name.asString() != "toString" || valueParameters.size != 0 || !returnType.isString())
+                    return false
+
+                return dispatchReceiverParameter == null
+                        && extensionReceiverParameter?.type?.isNullableAny() == true
+                        && fqNameWhenAvailable?.parent() == KotlinBuiltIns.BUILT_INS_PACKAGE_FQ_NAME
+            }
 
         /** @return true if the given expression is a call to [toString] */
-        private fun isToStringCall(expression: IrCall): Boolean {
+        private val IrCall.isToStringCall: Boolean
-            if (expression.superQualifierSymbol != null)
+            get() {
-                return false
+                if (superQualifierSymbol != null)
+                    return false
 
-            val function = expression.symbol.owner
+                val function = symbol.owner as? IrSimpleFunction
-            if (function.name.asString() != "toString" || function.valueParameters.size != 0 || !function.returnType.isString())
+                    ?: return false
-                return false
 
-            // Check for Any?.toString, which is an extension method defined in the kotlin package.
+                return function.isToString || function.isNullableToString
-            if (function.dispatchReceiverParameter == null
+            }
-                && function.extensionReceiverParameter?.type?.isNullableAny() == true
-                && function.fqNameWhenAvailable?.parent() == KotlinBuiltIns.BUILT_INS_PACKAGE_FQ_NAME)
-                return true
-
-            // Check for Any.toString or an override.
-            return (function.dispatchReceiverParameter != null && function.extensionReceiverParameter == null
-                    && (function.dispatchReceiverParameter?.type?.isAny() == true
-                    || (function as? IrSimpleFunction)?.overriddenSymbols?.isNotEmpty() == true))
-        }
 
         /** @return true if the given expression is a [IrStringConcatenation], or an [IrCall] to [toString] or [String.plus]. */
         private fun isStringConcatenationExpression(expression: IrExpression): Boolean =
-            (expression is IrStringConcatenation) || (expression is IrCall) && (isStringPlusCall(expression) || isToStringCall(expression))
+            (expression is IrStringConcatenation) || (expression is IrCall) && (expression.isStringPlusCall || expression.isToStringCall)
 
         /** Recursively collects string concatenation arguments from the given expression. */
         private fun collectStringConcatenationArguments(expression: IrExpression): List<IrExpression> {

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

@@ -218,6 +218,7 @@ private val jvmFilePhases =
         flattenStringConcatenationPhase then
         foldConstantLoweringPhase then
         computeStringTrimPhase then
+        jvmStringConcatenationLowering then
 
         defaultArgumentStubPhase then
         defaultArgumentInjectorPhase then

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

@@ -104,6 +104,10 @@ class JvmSymbols(
             addValueParameter("value", irBuiltIns.anyNType)
             addValueParameter("expression", irBuiltIns.stringType)
         }
+        klass.addFunction("stringPlus", irBuiltIns.stringType, isStatic = true).apply {
+            addValueParameter("self", irBuiltIns.stringType.makeNullable())
+            addValueParameter("other", irBuiltIns.anyNType)
+        }
     }
 
     val checkExpressionValueIsNotNull: IrSimpleFunctionSymbol =
@@ -115,6 +119,9 @@ class JvmSymbols(
     override val ThrowUninitializedPropertyAccessException: IrSimpleFunctionSymbol =
         intrinsicsClass.functions.single { it.owner.name.asString() == "throwUninitializedPropertyAccessException" }
 
+    val intrinsicStringPlus: IrFunctionSymbol =
+        intrinsicsClass.functions.single { it.owner.name.asString() == "stringPlus" }
+
     override val stringBuilder: IrClassSymbol
         get() = context.getTopLevelClass(FqName("java.lang.StringBuilder"))
 
@@ -437,9 +444,26 @@ class JvmSymbols(
             addValueParameter("v", irBuiltIns.anyNType)
             returnType = irBuiltIns.stringType
         }.symbol
+
+    private val javaLangString: IrClassSymbol = context.getTopLevelClass(FqName("java.lang.String"))
+
+    private val defaultValueOfFunction = javaLangString.functions.single {
+        it.owner.name.asString() == "valueOf" && it.owner.valueParameters.singleOrNull()?.type?.isNullableAny() == true
+    }
+
+    private val valueOfFunctions: Map<IrType, IrSimpleFunctionSymbol?> =
+        (context.irBuiltIns.primitiveIrTypes + context.irBuiltIns.stringType).associateWith { type ->
+            javaLangString.functions.singleOrNull {
+                it.owner.name.asString() == "valueOf" && it.owner.valueParameters.singleOrNull()?.type == type
+            }
+        }
+
+    fun typeToStringValueOfFunction(type: IrType): IrSimpleFunctionSymbol =
+        valueOfFunctions[type] ?: defaultValueOfFunction
 }
 
 private fun IrClassSymbol.functionByName(name: String): IrSimpleFunctionSymbol =
     functions.single { it.owner.name.asString() == name }
+
 private fun IrClassSymbol.fieldByName(name: String): IrFieldSymbol =
     fields.single { it.owner.name.asString() == name }

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt

@@ -671,54 +671,6 @@ class ExpressionCodegen(
         }
     }
 
-    override fun visitStringConcatenation(expression: IrStringConcatenation, data: BlockInfo): PromisedValue {
-        expression.markLineNumber(startOffset = true)
-        val arity = expression.arguments.size
-        when {
-            arity == 0 -> mv.aconst("")
-            arity == 1 -> {
-                // Convert single arg to string.
-                val arg = expression.arguments[0]
-                val result = arg.accept(this, data).boxInlineClasses(arg.type).materialized
-                if (!arg.type.isString()) {
-                    result.genToString(mv)
-                }
-            }
-            arity == 2 && expression.arguments[0].type.isStringClassType() -> {
-                // Call the stringPlus intrinsic
-                for ((index, argument) in expression.arguments.withIndex()) {
-                    val result = argument.accept(this, data).boxInlineClasses(argument.type).materialized
-                    if (result.type.sort != Type.OBJECT) {
-                        result.genToString(mv)
-                    } else if (index == 0) {
-                        result.coerce(context.irBuiltIns.stringType).materialize()
-                    }
-                }
-                mv.invokestatic(
-                    IrIntrinsicMethods.INTRINSICS_CLASS_NAME,
-                    "stringPlus",
-                    "(Ljava/lang/String;Ljava/lang/Object;)Ljava/lang/String;",
-                    false
-                )
-            }
-            else -> {
-                // Use StringBuilder to concatenate.
-                genStringBuilderConstructor(mv)
-                for (argument in expression.arguments) {
-                    genInvokeAppendMethod(mv, argument.accept(this, data).boxInlineClasses(argument.type).materialized.type, null)
-                }
-                mv.invokevirtual("java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false)
-            }
-        }
-        return expression.onStack
-    }
-
-    private fun MaterialValue.genToString(v: InstructionAdapter) {
-        val asmType =
-            if (irType.getClass()?.isInline == true) OBJECT_TYPE else stringValueOfType(type)
-        v.invokestatic("java/lang/String", "valueOf", Type.getMethodDescriptor(AsmTypes.JAVA_STRING_TYPE, asmType), false)
-    }
-
     override fun visitWhileLoop(loop: IrWhileLoop, data: BlockInfo): PromisedValue {
         val continueLabel = markNewLabel()
         val endLabel = Label()

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

@@ -0,0 +1,145 @@
+/*
+ * 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.phaser.makeIrFilePhase
+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.lower.inlineclasses.unboxInlineClass
+import org.jetbrains.kotlin.ir.builders.IrBuilderWithScope
+import org.jetbrains.kotlin.ir.builders.irCall
+import org.jetbrains.kotlin.ir.builders.irImplicitCast
+import org.jetbrains.kotlin.ir.builders.irString
+import org.jetbrains.kotlin.ir.declarations.IrClass
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrStringConcatenation
+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
+
+internal val jvmStringConcatenationLowering = makeIrFilePhase(
+    ::JvmStringConcatenationLowering,
+    name = "StringConcatenation",
+    description = "Replace IrStringConcatenation with string builders"
+)
+
+/**
+ * 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.
+ */
+private 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.size == 0
+    }
+
+    private val IrClass.toStringFunction: IrSimpleFunction
+        get() = functions.single {
+            with(FlattenStringConcatenationLowering) { it.isToString }
+        }
+
+    private val toStringFunction = stringBuilder.toStringFunction
+
+    private val defaultAppendFunction = stringBuilder.functions.single {
+        it.name.asString() == "append" &&
+                it.valueParameters.size == 1 &&
+                it.valueParameters.single().type.isNullableAny()
+    }
+
+    private val appendFunctions: Map<IrType, IrSimpleFunction?> =
+        (context.irBuiltIns.primitiveIrTypes + context.irBuiltIns.stringType).associateWith { type ->
+            stringBuilder.functions.singleOrNull {
+                it.name.asString() == "append" && it.valueParameters.singleOrNull()?.type == type
+            }
+        }
+
+    private fun typeToAppendFunction(type: IrType): IrSimpleFunction =
+        appendFunctions[type] ?: defaultAppendFunction
+
+    // There is no special append or valueOf function for byte and short on the JVM.
+    private fun IrBuilderWithScope.widenIntegerType(expression: IrExpression): IrExpression =
+        if (expression.type.isByte() || expression.type.isShort()) {
+            irImplicitCast(expression, context.irBuiltIns.intType)
+        } else {
+            expression
+        }
+
+    private fun JvmIrBuilder.callToString(expression: IrExpression): IrExpression {
+        if (expression.type.isString())
+            return expression
+
+        val argument = widenIntegerType(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.lowerInlineClassArgument(expression: IrExpression): IrExpression {
+        if (expression.type.unboxInlineClass() == expression.type)
+            return expression
+
+        val toStringFunction = expression.type.classOrNull?.owner?.toStringFunction
+            ?: return expression
+
+        val toStringReplacement = backendContext.inlineClassReplacements.getReplacementFunction(toStringFunction)
+            ?: return expression
+
+        return irCall(toStringReplacement.function).apply {
+            putValueArgument(0, expression)
+        }
+    }
+
+    override fun visitStringConcatenation(expression: IrStringConcatenation): IrExpression {
+        expression.transformChildrenVoid(this)
+        return context.createJvmIrBuilder(currentScope!!.scope.scopeOwnerSymbol, expression.startOffset, expression.endOffset).run {
+            val arguments = expression.arguments.map { lowerInlineClassArgument(it) }
+
+            when {
+                arguments.isEmpty() ->
+                    irString("")
+
+                arguments.size == 1 ->
+                    callToString(arguments.single())
+
+                arguments.size == 2 && arguments[0].type.isStringClassType() ->
+                    irCall(backendContext.ir.symbols.intrinsicStringPlus).apply {
+                        putValueArgument(0, arguments[0])
+                        putValueArgument(1, arguments[1])
+                    }
+
+                else -> {
+                    var stringBuilder = irCall(constructor)
+                    for (arg in arguments) {
+                        val argument = widenIntegerType(arg)
+                        val appendFunction = typeToAppendFunction(argument.type)
+                        stringBuilder = irCall(appendFunction).apply {
+                            dispatchReceiver = stringBuilder
+                            putValueArgument(0, argument)
+                        }
+                    }
+                    irCall(toStringFunction).apply {
+                        dispatchReceiver = stringBuilder
+                    }
+                }
+            }
+        }
+    }
+}

compiler/testData/codegen/bytecodeText/inlineClasses/inlineClassInGeneratedToString.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +InlineClasses
-// IGNORE_BACKEND: JVM_IR
 
 // FILE: Z.kt
 inline class Z(val value: Int)

compiler/testData/codegen/bytecodeText/inlineClasses/inlineClassInStringTemplate.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +InlineClasses
-// IGNORE_BACKEND: JVM_IR
 
 // FILE: Z.kt
 inline class Z(val value: Int)

compiler/testData/codegen/bytecodeText/inlineClasses/resultApiStringInterpolationDoesntBox.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 // WITH_RUNTIME
 // FILE: test.kt
 fun test() {