[IR] Avoid extra lists creation during getting explicit/all parameters (#3769)

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/ir/IrUtils.kt

@@ -11,7 +11,6 @@ import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
 import org.jetbrains.kotlin.descriptors.DescriptorVisibility
-import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.builders.Scope
@@ -432,14 +431,20 @@ fun IrFunction.createDispatchReceiverParameter(origin: IrDeclarationOrigin? = nu
 
 val IrFunction.allParameters: List<IrValueParameter>
     get() = if (this is IrConstructor) {
-        listOf(
+        ArrayList<IrValueParameter>(allParametersCount).also {
-            this.constructedClass.thisReceiver
+            it.add(
-                ?: error(this.render())
+                this.constructedClass.thisReceiver
-        ) + explicitParameters
+                    ?: error(this.render())
+            )
+            addExplicitParametersTo(it)
+        }
     } else {
         explicitParameters
     }
 
+val IrFunction.allParametersCount: Int
+    get() = if (this is IrConstructor) explicitParametersCount + 1 else explicitParametersCount
+
 private object FakeOverrideBuilder : FakeOverrideBuilderStrategy() {
     override fun linkFakeOverride(fakeOverride: IrOverridableMember) {
         when (fakeOverride) {

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

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.jvm.codegen
 
-import org.jetbrains.kotlin.backend.common.ir.allParameters
+import org.jetbrains.kotlin.backend.common.ir.allParametersCount
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
 import org.jetbrains.kotlin.backend.jvm.intrinsics.SignatureString
 import org.jetbrains.kotlin.backend.jvm.lower.FunctionReferenceLowering
@@ -64,7 +64,7 @@ class IrInlineIntrinsicsSupport(
         // thus cannot have a backing field, and is required to have a getter.
         val getter = property.getter
             ?: error("Property without getter: ${property.render()}")
-        val arity = getter.allParameters.size
+        val arity = getter.allParametersCount
         val implClass = (if (property.isVar) MUTABLE_PROPERTY_REFERENCE_IMPL else PROPERTY_REFERENCE_IMPL).getOrNull(arity)
             ?: error("No property reference impl class with arity $arity (${property.render()}")
 
@@ -77,7 +77,7 @@ class IrInlineIntrinsicsSupport(
         v.anew(implClass)
         v.dup()
         if (withArity) {
-            v.aconst(function.allParameters.size)
+            v.aconst(function.allParametersCount)
         }
         putClassInstance(v, FunctionReferenceLowering.getOwnerKClassType(declaration.parent, context))
         v.aconst(declaration.name.asString())

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

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.utils.DFS
+import org.jetbrains.kotlin.utils.addIfNotNull
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 /**
@@ -199,8 +200,22 @@ val IrClass.primaryConstructor: IrConstructor?
 val IrDeclarationContainer.properties: Sequence<IrProperty>
     get() = declarations.asSequence().filterIsInstance<IrProperty>()
 
+fun IrFunction.addExplicitParametersTo(parametersList: MutableList<IrValueParameter>) {
+    parametersList.addIfNotNull(dispatchReceiverParameter)
+    parametersList.addIfNotNull(extensionReceiverParameter)
+    parametersList.addAll(valueParameters)
+}
+
+private fun Boolean.toInt(): Int = if (this) 1 else 0
+
+val IrFunction.explicitParametersCount: Int
+    get() = (dispatchReceiverParameter != null).toInt() + (extensionReceiverParameter != null).toInt() +
+            valueParameters.size
+
 val IrFunction.explicitParameters: List<IrValueParameter>
-    get() = (listOfNotNull(dispatchReceiverParameter, extensionReceiverParameter) + valueParameters)
+    get() = ArrayList<IrValueParameter>(explicitParametersCount).also {
+        addExplicitParametersTo(it)
+    }
 
 val IrBody.statements: List<IrStatement>
     get() = when (this) {