[K/Wasm] Convert non-capturing lambdas into singletons ^KT-64803 Fixed

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/WasmLoweringPhases.kt

@@ -286,7 +286,6 @@ private val singleAbstractMethodPhase = makeIrModulePhase(
     description = "Replace SAM conversions with instances of interface-implementing classes"
 )
 
-
 private val localDelegatedPropertiesLoweringPhase = makeIrModulePhase<WasmBackendContext>(
     { LocalDelegatedPropertiesLowering() },
     name = "LocalDelegatedPropertiesLowering",
@@ -307,6 +306,13 @@ private val localClassExtractionPhase = makeIrModulePhase(
     prerequisite = setOf(localDeclarationsLoweringPhase)
 )
 
+private val staticCallableReferenceLoweringPhase = makeIrModulePhase(
+    ::WasmStaticCallableReferenceLowering,
+    name = "WasmStaticCallableReferenceLowering",
+    description = "Turn static callable references into singletons",
+    prerequisite = setOf(callableReferencePhase, localClassExtractionPhase)
+)
+
 private val innerClassesLoweringPhase = makeIrModulePhase<WasmBackendContext>(
     { context -> InnerClassesLowering(context, context.innerClassesSupport) },
     name = "InnerClassesLowering",
@@ -653,6 +659,7 @@ val loweringList = listOf(
     localDelegatedPropertiesLoweringPhase,
     localDeclarationsLoweringPhase,
     localClassExtractionPhase,
+    staticCallableReferenceLoweringPhase,
     innerClassesLoweringPhase,
     innerClassesMemberBodyLoweringPhase,
     innerClassConstructorCallsLoweringPhase,

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/dce/WasmUsefulDeclarationProcessor.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.backend.wasm.dce
 
 import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
 import org.jetbrains.kotlin.backend.wasm.ir2wasm.*
+import org.jetbrains.kotlin.backend.wasm.lower.isFunctionReferenceInstanceField
 import org.jetbrains.kotlin.backend.wasm.utils.*
 import org.jetbrains.kotlin.ir.backend.js.dce.UsefulDeclarationProcessor
 import org.jetbrains.kotlin.ir.backend.js.utils.*
@@ -48,7 +49,7 @@ internal class WasmUsefulDeclarationProcessor(
         }
 
         override fun visitSetField(expression: IrSetField, data: IrDeclaration) {
-            if (!expression.symbol.owner.isObjectInstanceField()) {
+            if (!expression.symbol.owner.run { isObjectInstanceField() || isFunctionReferenceInstanceField() }) {
                 super.visitSetField(expression, data)
             }
         }
@@ -56,7 +57,7 @@ internal class WasmUsefulDeclarationProcessor(
         override fun visitGetField(expression: IrGetField, data: IrDeclaration) {
             val field = expression.symbol.owner
 
-            if (field.isObjectInstanceField()) {
+            if (field.isObjectInstanceField() || field.isFunctionReferenceInstanceField()) {
                 field.type.classOrFail.owner.primaryConstructor?.enqueue(field, "object lazy initialization")
             }
 

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/dce/WasmUselessDeclarationsRemover.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.backend.wasm.dce
 
 import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
+import org.jetbrains.kotlin.backend.wasm.lower.isFunctionReferenceInstanceField
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.backend.js.utils.isObjectInstanceField
 import org.jetbrains.kotlin.ir.declarations.*
@@ -56,7 +57,7 @@ class WasmUselessDeclarationsRemover(
 
     private fun IrSimpleFunction.removeUnusedObjectsInitializers() {
         (body as? IrBlockBody)?.statements?.removeIf {
-            it is IrSetField && it.symbol.owner.isObjectInstanceField() && it.symbol.owner !in usefulDeclarations
+            it is IrSetField && it.symbol.owner.run { isObjectInstanceField() || isFunctionReferenceInstanceField() } && it.symbol.owner !in usefulDeclarations
         }
     }
 }

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/lower/WasmPropertyReferenceLowering.kt

@@ -310,7 +310,7 @@ internal class WasmPropertyReferenceLowering(val context: WasmBackendContext) :
         return type.classifier == expectedClass
     }
 
-    private companion object {
-        private val DECLARATION_ORIGIN_KPROPERTIES_FOR_DELEGATION = IrDeclarationOriginImpl("KPROPERTIES_FOR_DELEGATION")
+    companion object {
+        val DECLARATION_ORIGIN_KPROPERTIES_FOR_DELEGATION = IrDeclarationOriginImpl("KPROPERTIES_FOR_DELEGATION")
     }
 }

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/lower/WasmStaticCallableReferenceLowering.kt

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2010-2024 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.wasm.lower
+
+import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.backend.common.getOrPut
+import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
+import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
+import org.jetbrains.kotlin.backend.wasm.lower.WasmPropertyReferenceLowering.Companion.DECLARATION_ORIGIN_KPROPERTIES_FOR_DELEGATION
+import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
+import org.jetbrains.kotlin.ir.IrStatement
+import org.jetbrains.kotlin.ir.backend.js.lower.CallableReferenceLowering.Companion.FUNCTION_REFERENCE_IMPL
+import org.jetbrains.kotlin.ir.backend.js.lower.CallableReferenceLowering.Companion.LAMBDA_IMPL
+import org.jetbrains.kotlin.ir.builders.declarations.buildField
+import org.jetbrains.kotlin.ir.builders.irCall
+import org.jetbrains.kotlin.ir.builders.irExprBody
+import org.jetbrains.kotlin.ir.declarations.*
+import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.impl.IrGetFieldImpl
+import org.jetbrains.kotlin.ir.types.makeNullable
+import org.jetbrains.kotlin.ir.util.constructedClass
+import org.jetbrains.kotlin.ir.util.defaultType
+import org.jetbrains.kotlin.ir.util.primaryConstructor
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
+import org.jetbrains.kotlin.name.Name
+
+class WasmStaticCallableReferenceLowering(val context: WasmBackendContext) : FileLoweringPass {
+    override fun lower(irFile: IrFile) {
+        val irFields = mutableSetOf<IrField>()
+        val firstKProperty = irFile.declarations.indexOfFirst { it.origin == DECLARATION_ORIGIN_KPROPERTIES_FOR_DELEGATION }
+
+        irFile.transformChildrenVoid(object : IrElementTransformerVoid() {
+            override fun visitClass(declaration: IrClass): IrStatement {
+                declaration.transformChildrenVoid()
+                if (declaration.isSyntheticSingleton) {
+                    val functionReferenceField = declaration.getOrCreateInstanceField().apply {
+                        parent = irFile
+                        initializer = context.createIrBuilder(symbol).run {
+                            irExprBody(irCall(declaration.primaryConstructor!!))
+                        }
+                    }
+                    irFields.add(functionReferenceField)
+                }
+                return declaration
+            }
+
+            override fun visitConstructorCall(expression: IrConstructorCall): IrExpression {
+                val constructedClass = expression.symbol.owner.constructedClass
+                if (!constructedClass.isSyntheticSingleton)
+                    return super.visitConstructorCall(expression)
+
+                val instanceField = constructedClass.getOrCreateInstanceField()
+                return IrGetFieldImpl(expression.startOffset, expression.endOffset, instanceField.symbol, expression.type)
+            }
+        })
+
+        // Should be placed before KProperty initializations
+        if (firstKProperty != -1) {
+            irFile.declarations.addAll(firstKProperty, irFields)
+        } else {
+            irFile.declarations.addAll(irFields)
+        }
+    }
+
+
+    private fun IrClass.getOrCreateInstanceField(): IrField = context.mapping.functionToInstanceField.getOrPut(this) {
+        val klass = this
+        context.irFactory.buildField {
+            name = Name.identifier(klass.name.asString() + "_instance")
+            type = klass.defaultType.makeNullable()
+            isStatic = true
+            isFinal = true
+            origin = FUNCTION_REFERENCE_SINGLETON_FIELD
+            visibility = DescriptorVisibilities.PRIVATE
+        }.apply {
+            initializer = null
+        }
+    }
+}
+
+val FUNCTION_REFERENCE_SINGLETON_FIELD by IrDeclarationOriginImpl
+
+fun IrField.isFunctionReferenceInstanceField(): Boolean {
+    return origin == FUNCTION_REFERENCE_SINGLETON_FIELD
+}
+
+val IrClass.isSyntheticSingleton: Boolean
+    get() = (origin == LAMBDA_IMPL || origin == FUNCTION_REFERENCE_IMPL) && primaryConstructor!!.valueParameters.isEmpty()