IR: optimize transformation of declarations/statements lists in-place

Also, inherit IrDeclarationBase from IrElementBase to be able to use a
cast to IrElementBase, which is faster than a cast to IrElement or
IrDeclaration.

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/IrClass.kt

@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.descriptors.SourceElement
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.types.IrType
-import org.jetbrains.kotlin.ir.util.transform
+import org.jetbrains.kotlin.ir.util.transformInPlace
 import org.jetbrains.kotlin.ir.util.transformIfNeeded
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
@@ -63,7 +63,7 @@ abstract class IrClass :
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
         thisReceiver = thisReceiver?.transform(transformer, data)
         typeParameters = typeParameters.transformIfNeeded(transformer, data)
-        declarations.transform { it.transform(transformer, data) }
+        declarations.transformInPlace(transformer, data)
     }
 }
 

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/IrDeclaration.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibility
 import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.IrElementBase
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.symbols.IrSymbol
@@ -45,7 +46,7 @@ interface IrDeclaration : IrStatement, IrMutableAnnotationContainer {
     val factory: IrFactory
 }
 
-abstract class IrDeclarationBase : IrDeclaration {
+abstract class IrDeclarationBase : IrElementBase(), IrDeclaration {
     override fun <D> transform(transformer: IrElementTransformer<D>, data: D): IrStatement =
         accept(transformer, data) as IrStatement
 }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrScriptImpl.kt

@@ -12,7 +12,7 @@ import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
 import org.jetbrains.kotlin.ir.symbols.IrScriptSymbol
-import org.jetbrains.kotlin.ir.util.transform
+import org.jetbrains.kotlin.ir.util.transformInPlace
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
@@ -65,8 +65,8 @@ class IrScriptImpl(
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-        declarations.transform { it.transform(transformer, data) }
-        statements.transform { it.transform(transformer, data) }
+        declarations.transformInPlace(transformer, data)
+        statements.transformInPlace(transformer, data)
         thisReceiver = thisReceiver.transform(transformer, data)
     }
 }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/expressions/IrBlock.kt

@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.ir.symbols.IrFileSymbol
 import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
 import org.jetbrains.kotlin.ir.symbols.IrReturnableBlockSymbol
 import org.jetbrains.kotlin.ir.util.file
-import org.jetbrains.kotlin.ir.util.transform
+import org.jetbrains.kotlin.ir.util.transformInPlace
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 
@@ -38,7 +38,7 @@ abstract class IrContainerExpression : IrExpression(), IrStatementContainer {
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-        statements.transform { it.transform(transformer, data) }
+        statements.transformInPlace(transformer, data)
     }
 }
 
@@ -58,5 +58,6 @@ abstract class IrReturnableBlock : IrBlock(), IrSymbolOwner, IrReturnTarget {
     abstract val inlineFunctionSymbol: IrFunctionSymbol?
 }
 
+@Suppress("unused") // Used in kotlin-native
 val IrReturnableBlock.sourceFileSymbol: IrFileSymbol?
     get() = inlineFunctionSymbol?.owner?.file?.symbol

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/transform.kt

@@ -17,13 +17,22 @@
 package org.jetbrains.kotlin.ir.util
 
 import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.IrElementBase
 import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.declarations.IrDeclarationContainer
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 
-inline fun <reified T : IrElement> MutableList<T>.transform(transformation: (T) -> IrElement) {
-    forEachIndexed { i, item ->
-        set(i, transformation(item) as T)
+inline fun <reified T : IrElement> MutableList<T>.transformInPlace(transformation: (T) -> IrElement) {
+    for (i in 0 until size) {
+        set(i, transformation(get(i)) as T)
+    }
+}
+
+fun <T : IrElement, D> MutableList<T>.transformInPlace(transformer: IrElementTransformer<D>, data: D) {
+    for (i in 0 until size) {
+        // Cast to IrElementBase to avoid casting to interface and invokeinterface, both of which are slow.
+        @Suppress("UNCHECKED_CAST")
+        set(i, (get(i) as IrElementBase).transform(transformer, data) as T)
     }
 }