Lambda memoization doesn't work with Kotlin/Compose compiler 2.0.0-RC3 [340582180]

Fixed

Bug

Status Update

No update yet.

Description

sp...@gmail.com

created issue #1

May 15, 2024 06:43AM

Jetpack Compose compiler version: 2.0.0-RC3

Jetpack Compose version: 1.6.10-rc02 (KMP)

Android Studio Build: Android Studio Jellyfish | 2023.3.1

Kotlin version: 2.0.0-RC3

Steps to Reproduce or Code Sample to Reproduce:

Create sample project from kmp.jetbrains.com
Bump kotlin and compose compiler version to 2.0.0-RC3 (link)
Replace code in App.kt:

@Composable
fun App() {
    MaterialTheme {
        var someBoolState = remember { mutableStateOf(false) }
        Column {
            Test(someBoolState.value)
            Button(onClick = { someBoolState.value = !someBoolState.value }) {
                Text("Click me!")
            }
        }
    }
}

@Composable
fun Test(
    someBool: Boolean,
) {
    val lambda = test2(someBool)
    Text(lambda.hashCode().toString())
}

@Composable
fun test2(
    someBool: Boolean,
    argLambda: () -> Boolean = { true },
): SomeState {
    println("TEST123 ${argLambda.toString()} ${argLambda.hashCode().toString()} $someBool")
    return remember(argLambda) { SomeState(argLambda) }
}

@Immutable
class SomeState(val lambda: () -> Boolean)

Log output:

2.0.0-RC3
TEST123 AppKt$$ExternalSyntheticLambda1@a598d7a 173641082 false
TEST123 AppKt$$ExternalSyntheticLambda1@ebb39f 15446943 true

kotlin 1.9.23
TEST123 Function0<java.lang.Boolean> 53959439 true
TEST123 Function0<java.lang.Boolean> 53959439 false

For Compose Multiplatform 1.6.2 and kotlin 1.9.23 lambda memoization works.

Comments

as...@google.com <as...@google.com> #2May 15, 2024 04:48PM

It seems like Kotlin compiler used to generate a static field for each lambda that doesn't capture any parameters before K2. With K2, the compiler generates invokedynamic, which is desugared into creating a new object each time on Android. I assume that this should not be a problem for JDK that properly supports invokedynamic (e.g. desktop), but we likely want to hoist these functions in Compose compiler if Kotlin compiler is not going to do so.

Message last modified on May 15, 2024 04:48PM

ch...@google.com <ch...@google.com> #3May 15, 2024 05:01PM

Alternately we can remember them by not special cases non-capturing lambdas.

as...@google.com <as...@google.com> #4May 15, 2024 05:13PM

Reassigned to as...@google.com.

I think it is more useful to hoist them to avoid taking up space in slot table.

ko...@dumps.app <ko...@dumps.app> #5May 23, 2024 09:31PM

I also ran into this trying out K2. I was relying on a lambda being stable as a key for remembering a state object. In code that's similar to rememberModalBottomSheetState

sp...@gmail.com <sp...@gmail.com> #6May 24, 2024 01:07PM

I didn’t write it, but initially I also had this problem with BottomSheet in material 3 with the confirmValueChange lambda parameter.

ap...@google.com <ap...@google.com> #7May 28, 2024 10:15PM

Marked as fixed.

Project: platform/frameworks/support
Branch: androidx-main

commit 0428c00d04376c0d2bb7130ff3410db1b3238da2
Author: Andrei Shikov <ashikov@google.com>
Date: Tue May 28 16:35:51 2024

Memoize non-capturing lambdas when K2 is enabled

K2 uses invokedynamic for lambdas and D8 does not optimize capture-less generated instances on Android as K1 used to.

Fixes: 340582180
Test: compiler tests
Relnote: "Fix memoization of captureless lambdas when K2 compiler is used"
Change-Id: I71c91882d0cdcbe88e0086bc4a14b3e9825383bc

M compose/compiler/compiler-hosted/integration-tests/src/jvmTest/kotlin/androidx/compose/compiler/plugins/kotlin/AbstractCodegenSignatureTest.kt
M compose/compiler/compiler-hosted/integration-tests/src/jvmTest/kotlin/androidx/compose/compiler/plugins/kotlin/ComposerParamSignatureTests.kt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.ComposerParamSignatureTests/testDexNaming[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.ComposerParamSignatureTests/testFunInterfacesInComposableCall[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.ComposerParamSignatureTests/testLambdaReorderedParameter[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.ComposerParamTransformTests/composableLocalFunctionInsideLocalClass[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.ComposerParamTransformTests/testDexNaming[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.ControlFlowTransformTests/testRepeatedCallsToEffects[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.FunctionBodySkippingTransformTests/testBasicText[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.FunctionBodySkippingTransformTests/testStaticDetection[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.FunctionalInterfaceTransformTests/testNoCaptureFunInterface[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.LambdaMemoizationTransformTests/testFunctionReferenceWithinInferredComposableLambda[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.LambdaMemoizationTransformTests/testLambdaNoCapture[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.LambdaMemoizationTransformTests/testLocalFunCaptures[useFir = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.StrongSkippingModeTransformTests/testFunctionInterfaceMemorized[useFir = true, intrinsicRemember = false].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.StrongSkippingModeTransformTests/testFunctionInterfaceMemorized[useFir = true, intrinsicRemember = true].txt
M compose/compiler/compiler-hosted/integration-tests/src/test/resources/golden/androidx.compose.compiler.plugins.kotlin.TargetAnnotationsTransformTests/testCallingLayout[useFir = true].txt
M compose/compiler/compiler-hosted/src/main/java/androidx/compose/compiler/plugins/kotlin/lower/ComposerLambdaMemoization.kt

https://android-review.googlesource.com/3106299

Issue 340582180