JVM IR: inherit some lowerings from ClassLoweringPass

This slightly simplifies code, but has no other immediate benefits. In
the future though, we may end up optimizing all ClassLoweringPass
JVM IR phases by making them traverse only one list of all classes in
the module, instead of traversing the whole IR tree each time.

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

@@ -5,16 +5,12 @@
 
 package org.jetbrains.kotlin.backend.jvm.lower
 
-import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.backend.common.ClassLoweringPass
 import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
-import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.declarations.IrClass
 import org.jetbrains.kotlin.ir.declarations.IrConstructor
-import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.util.isAnnotationClass
-import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
-import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 
 internal val annotationPhase = makeIrFilePhase<JvmBackendContext>(
     { AnnotationLowering() },
@@ -22,13 +18,10 @@ internal val annotationPhase = makeIrFilePhase<JvmBackendContext>(
     description = "Remove constructors of annotation classes"
 )
 
-private class AnnotationLowering : FileLoweringPass, IrElementTransformerVoid() {
-    override fun lower(irFile: IrFile) = irFile.transformChildrenVoid(this)
-
-    override fun visitClass(declaration: IrClass): IrStatement =
-        declaration.transformPostfix {
-            if (isAnnotationClass) {
-                declarations.removeIf { it is IrConstructor }
-            }
+private class AnnotationLowering : ClassLoweringPass {
+    override fun lower(irClass: IrClass) {
+        if (irClass.isAnnotationClass) {
+            irClass.declarations.removeIf { it is IrConstructor }
         }
+    }
 }

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

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.jvm.lower
 
-import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.backend.common.ClassLoweringPass
 import org.jetbrains.kotlin.backend.common.lower.SpecialMethodWithDefaultInfo
 import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
 import org.jetbrains.kotlin.backend.common.lower.irNot
@@ -18,7 +18,6 @@ import org.jetbrains.kotlin.backend.jvm.ir.*
 import org.jetbrains.kotlin.codegen.AsmUtil
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
 import org.jetbrains.kotlin.descriptors.Modality
-import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.builders.declarations.addFunction
 import org.jetbrains.kotlin.ir.declarations.*
@@ -30,7 +29,6 @@ import org.jetbrains.kotlin.ir.types.isNullable
 import org.jetbrains.kotlin.ir.types.isPrimitiveType
 import org.jetbrains.kotlin.ir.types.makeNullable
 import org.jetbrains.kotlin.ir.util.*
-import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.utils.SmartList
 import org.jetbrains.org.objectweb.asm.Type
@@ -118,7 +116,7 @@ internal val bridgePhase = makeIrFilePhase(
     prerequisite = setOf(jvmValueClassPhase, inheritedDefaultMethodsOnClassesPhase)
 )
 
-internal class BridgeLowering(val context: JvmBackendContext) : FileLoweringPass, IrElementTransformerVoid() {
+internal class BridgeLowering(val context: JvmBackendContext) : ClassLoweringPass {
     // Represents a synthetic bridge to `overridden` with a precomputed signature
     private class Bridge(
         val overridden: IrSimpleFunction,
@@ -126,27 +124,21 @@ internal class BridgeLowering(val context: JvmBackendContext) : FileLoweringPass
         val overriddenSymbols: MutableList<IrSimpleFunctionSymbol> = mutableListOf()
     )
 
-    override fun lower(irFile: IrFile) {
-        irFile.transformChildrenVoid()
-    }
+    override fun lower(irClass: IrClass) {
+        // Bridges in DefaultImpls classes are handled in InterfaceLowering.
+        if (irClass.origin == JvmLoweredDeclarationOrigin.DEFAULT_IMPLS || irClass.isAnnotationClass) return
 
-    override fun visitClass(declaration: IrClass): IrStatement {
-        // Bridges in DefaultImpl classes are handled in InterfaceLowering.
-        if (declaration.origin == JvmLoweredDeclarationOrigin.DEFAULT_IMPLS || declaration.isAnnotationClass)
-            return super.visitClass(declaration)
+        val bridgeTargets = irClass.functions.filterTo(SmartList()) { it.isPotentialBridgeTarget() }
+        if (bridgeTargets.isEmpty()) return
 
-        val bridgeTargets = declaration.functions.filterTo(SmartList()) { it.isPotentialBridgeTarget() }
-        if (bridgeTargets.isEmpty())
-            return super.visitClass(declaration)
+        bridgeTargets.forEach { createBridges(irClass, it) }
 
-        bridgeTargets.forEach { createBridges(declaration, it) }
-
-        if (declaration.isSingleFieldValueClass) {
+        if (irClass.isSingleFieldValueClass) {
             // Inline class (implementing 'MutableCollection<T>', where T is Int or an inline class mapped to Int)
             // can contain a static replacement for a function 'remove', which forces value parameter boxing
             // in order to avoid signature clash with 'remove(int)' method in 'java.util.List'.
             // We should rewrite this static replacement as well ('remove' function itself is handled during special bridge processing).
-            val remove = declaration.functions.find {
+            val remove = irClass.functions.find {
                 val original = context.inlineClassReplacements.originalFunctionForStaticReplacement[it]
                 original != null && context.defaultMethodSignatureMapper.shouldBoxSingleValueParameterForSpecialCaseOfRemove(original)
             }
@@ -156,8 +148,6 @@ internal class BridgeLowering(val context: JvmBackendContext) : FileLoweringPass
                 }
             }
         }
-
-        return super.visitClass(declaration)
     }
 
     private fun IrSimpleFunction.isPotentialBridgeTarget(): Boolean {

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

@@ -28,7 +28,9 @@ import org.jetbrains.kotlin.ir.expressions.impl.IrTypeOperatorCallImpl
 import org.jetbrains.kotlin.ir.expressions.putArgument
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.*
-import org.jetbrains.kotlin.ir.visitors.*
+import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
+import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
+import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 
 internal val inheritedDefaultMethodsOnClassesPhase = makeIrFilePhase(
     ::InheritedDefaultMethodsOnClassesLowering,
@@ -123,25 +125,24 @@ internal val replaceDefaultImplsOverriddenSymbolsPhase = makeIrFilePhase(
     description = "Replace overridden symbols for methods inherited from interfaces to classes"
 )
 
-private class ReplaceDefaultImplsOverriddenSymbols(private val context: JvmBackendContext) : FileLoweringPass, IrElementVisitorVoid {
-    override fun lower(irFile: IrFile) {
-        irFile.acceptVoid(this)
-    }
-
-    override fun visitElement(element: IrElement) {
-        element.acceptChildrenVoid(this)
+private class ReplaceDefaultImplsOverriddenSymbols(private val context: JvmBackendContext) : ClassLoweringPass {
+    override fun lower(irClass: IrClass) {
+        for (declaration in irClass.declarations) {
+            if (declaration is IrSimpleFunction) {
+                visitSimpleFunction(declaration)
+            }
+        }
     }
 
     // Functions introduced by InheritedDefaultMethodsOnClassesLowering may be inherited lower in the hierarchy.
     // Here we use the same logic as the delegation itself (`getTargetForRedirection`) to determine
     // if the overridden symbol has been, or will be, replaced and patch it accordingly.
-    override fun visitSimpleFunction(declaration: IrSimpleFunction) {
+    fun visitSimpleFunction(declaration: IrSimpleFunction) {
         declaration.overriddenSymbols = declaration.overriddenSymbols.map { symbol ->
             if (symbol.owner.findInterfaceImplementation(context.config.jvmDefaultMode) != null)
                 context.cachedDeclarations.getDefaultImplsRedirection(symbol.owner).symbol
             else symbol
         }
-        super.visitSimpleFunction(declaration)
     }
 }
 

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

@@ -5,15 +5,13 @@
 
 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.ClassLoweringPass
 import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
 import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
 import org.jetbrains.kotlin.backend.jvm.ir.createJvmIrBuilder
 import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
-import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.builders.irCall
 import org.jetbrains.kotlin.ir.builders.irExprBody
 import org.jetbrains.kotlin.ir.builders.irGetField
@@ -31,23 +29,17 @@ internal val objectClassPhase = makeIrFilePhase(
     description = "Handle object classes"
 )
 
-private class ObjectClassLowering(val context: JvmBackendContext) : IrElementTransformerVoidWithContext(), FileLoweringPass {
-
-    private var pendingTransformations = mutableListOf<Function0<Unit>>()
+private class ObjectClassLowering(val context: JvmBackendContext) : ClassLoweringPass {
+    private val pendingTransformations = mutableListOf<Function0<Unit>>()
 
     override fun lower(irFile: IrFile) {
-        irFile.accept(this, null)
-
-        pendingTransformations.forEach { it() }
+        super.lower(irFile)
+        for (transformation in pendingTransformations) {
+            transformation.invoke()
+        }
     }
 
-    override fun visitClassNew(declaration: IrClass): IrStatement {
-        process(declaration)
-        return super.visitClassNew(declaration)
-    }
-
-
-    private fun process(irClass: IrClass) {
+    override fun lower(irClass: IrClass) {
         if (!irClass.isObject) return
 
         val publicInstanceField = context.cachedDeclarations.getFieldForObjectInstance(irClass)