IR: move defaultParameterDeclarationsCache access up one level

to avoid recomputing overriddenSymbols for fake overrides of default
stubs on repeated calls to generateDefaultsFunction.

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

@@ -312,11 +312,13 @@ private fun IrFunction.generateDefaultsFunction(
     context: CommonBackendContext,
     skipInlineMethods: Boolean,
     skipExternalMethods: Boolean
-): IrFunction? = when {
+): IrFunction? = context.ir.defaultParameterDeclarationsCache[this] ?: when {
     skipInlineMethods && isInline -> null
     skipExternalMethods && isExternalOrInheritedFromExternal() -> null
     valueParameters.any { it.defaultValue != null } ->
-        generateDefaultsFunctionImpl(context, IrDeclarationOrigin.FUNCTION_FOR_DEFAULT_PARAMETER)
+        generateDefaultsFunctionImpl(context, IrDeclarationOrigin.FUNCTION_FOR_DEFAULT_PARAMETER).also {
+            context.ir.defaultParameterDeclarationsCache[this] = it
+        }
     this is IrSimpleFunction -> {
         // If this is an override of a function with default arguments, produce a fake override of a default stub.
         val overriddenStubs = overriddenSymbols.mapNotNull {
@@ -325,6 +327,7 @@ private fun IrFunction.generateDefaultsFunction(
         if (overriddenStubs.isNotEmpty())
             generateDefaultsFunctionImpl(context, IrDeclarationOrigin.FAKE_OVERRIDE).also {
                 (it as IrSimpleFunction).overriddenSymbols.addAll(overriddenStubs)
+                context.ir.defaultParameterDeclarationsCache[this] = it
             }
         else
             null
@@ -332,8 +335,7 @@ private fun IrFunction.generateDefaultsFunction(
     else -> null
 }
 
-private fun IrFunction.generateDefaultsFunctionImpl(context: CommonBackendContext, newOrigin: IrDeclarationOrigin): IrFunction =
-    context.ir.defaultParameterDeclarationsCache.getOrPut(this) {
+private fun IrFunction.generateDefaultsFunctionImpl(context: CommonBackendContext, newOrigin: IrDeclarationOrigin): IrFunction {
     val newFunction = when (this) {
         is IrConstructor ->
             buildConstructor {
@@ -379,5 +381,5 @@ private fun IrFunction.generateDefaultsFunctionImpl(context: CommonBackendContex
 
     // TODO some annotations are needed (e.g. @JvmStatic), others need different values (e.g. @JvmName), the rest are redundant.
     annotations.mapTo(newFunction.annotations) { it.deepCopyWithSymbols() }
-        newFunction
+    return newFunction
 }