[Wasm] Add an option to dump reachability info to file

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt

@@ -294,6 +294,20 @@ class K2JSCompilerArguments : CommonCompilerArguments() {
             field = value
         }
 
+    @Argument(
+        value = "-Xir-dce-dump-reachability-info-to-file",
+        valueDescription = "<path>",
+        description = "Dump declarations' reachability info collected during performing DCE to a file. " +
+                "The format will be chosen automatically based on the file extension. " +
+                "Supported output formats include JSON for .json, JS const initialized with a plain object containing information for .js, " +
+                "and plain text for all other file types."
+    )
+    var irDceDumpReachabilityInfoToFile: String? = null
+        set(value) {
+            checkFrozen()
+            field = value
+        }
+
     @Argument(value = "-Xir-property-lazy-initialization", description = "Perform lazy initialization for properties")
     var irPropertyLazyInitialization = true
         set(value) {

compiler/cli/cli-js/src/org/jetbrains/kotlin/cli/js/K2JsIrCompiler.kt

@@ -723,6 +723,7 @@ class K2JsIrCompiler : CLICompiler<K2JSCompilerArguments>() {
 
         configuration.put(JSConfigurationKeys.PRINT_REACHABILITY_INFO, arguments.irDcePrintReachabilityInfo)
         configuration.put(JSConfigurationKeys.FAKE_OVERRIDE_VALIDATOR, arguments.fakeOverrideValidator)
+        configuration.putIfNotNull(JSConfigurationKeys.DUMP_REACHABILITY_INFO_TO_FILE, arguments.irDceDumpReachabilityInfoToFile)
 
         configuration.setupPartialLinkageConfig(
             mode = arguments.partialLinkageMode,

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UsefulDeclarationProcessor.kt

@@ -16,11 +16,13 @@ import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.types.classifierOrNull
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
+import java.io.File
 import java.util.*
 
 abstract class UsefulDeclarationProcessor(
     private val printReachabilityInfo: Boolean,
-    protected val removeUnusedAssociatedObjects: Boolean
+    protected val removeUnusedAssociatedObjects: Boolean,
+    private val dumpReachabilityInfoToFile: String? = null
 ) {
     abstract val context: JsCommonBackendContext
 
@@ -85,12 +87,7 @@ abstract class UsefulDeclarationProcessor(
         description: String?,
         isContagiousOverridableDeclaration: Boolean,
     ) {
-        if (!printReachabilityInfo) return
+        reachabilityInfos?.add(ReachabilityInfo(from, to, description, isContagiousOverridableDeclaration))
-        val fromFqn = (from as? IrDeclarationWithName)?.fqNameWhenAvailable?.asString() ?: "<unknown>"
-        val toFqn = (to as? IrDeclarationWithName)?.fqNameWhenAvailable?.asString() ?: "<unknown>"
-        val comment = (description ?: "") + (if (isContagiousOverridableDeclaration) "[CONTAGIOUS!]" else "")
-        val info = "\"$fromFqn\" -> \"$toFqn\"" + (if (comment.isBlank()) "" else " // $comment")
-        reachabilityInfo.add(info)
     }
 
     protected fun IrDeclaration.enqueue(
@@ -133,11 +130,12 @@ abstract class UsefulDeclarationProcessor(
     //
     // The collection must be a subset of [result] set.
     private val contagiousReachableDeclarations = hashSetOf<IrOverridableDeclaration<*>>()
-    protected val constructedClasses = hashSetOf<IrClass>()
+    protected val constructedClasses = linkedSetOf<IrClass>()
-    private val reachabilityInfo: MutableSet<String> = if (printReachabilityInfo) linkedSetOf() else Collections.emptySet()
+    private val reachabilityInfos =
+        if (printReachabilityInfo || dumpReachabilityInfoToFile != null) mutableListOf<ReachabilityInfo>() else null
     private val queue = ArrayDeque<IrDeclaration>()
     protected val result = hashSetOf<IrDeclaration>()
-    protected val classesWithObjectAssociations = hashSetOf<IrClass>()
+    protected val classesWithObjectAssociations = linkedSetOf<IrClass>()
 
     val usefulPolyfilledDeclarations = hashSetOf<IrDeclaration>()
 
@@ -268,10 +266,70 @@ abstract class UsefulDeclarationProcessor(
             }
         }
 
-        if (printReachabilityInfo) {
+        if (reachabilityInfos != null) {
-            reachabilityInfo.forEach(::println)
+            if (printReachabilityInfo) {
+                println(transformToDotLikeString(reachabilityInfos))
+            }
+
+            if (dumpReachabilityInfoToFile != null) {
+                val out = File(dumpReachabilityInfoToFile)
+                val stringify = when (out.extension) {
+                    "json" -> ::transformToJsonString
+                    "js" -> ::transformToJsConstDeclaration
+                    else -> ::transformToDotLikeString
+                }
+
+                out.writeText(stringify(reachabilityInfos))
+            }
         }
 
         return result
     }
-}
+}
+
+private data class ReachabilityInfo(
+    val source: IrDeclaration,
+    val target: IrDeclaration,
+    val description: String?,
+    val isTargetContagious: Boolean
+)
+
+private fun transformToStringBy(
+    reachabilityInfos: List<ReachabilityInfo>,
+    separator: String,
+    transformer: (sourceFqn: String, targetFqn: String, description: String, isTargetContagious: Boolean) -> String
+): String {
+    fun IrDeclaration.fqnOrUnknown() = (this as? IrDeclarationWithName)?.fqNameWhenAvailable?.asString() ?: "<unknown>"
+
+    return reachabilityInfos
+        .map {
+            transformer(it.source.fqnOrUnknown(), it.target.fqnOrUnknown(), it.description ?: "", it.isTargetContagious)
+        }
+        .distinct()
+        .joinToString(separator)
+}
+
+private fun transformToDotLikeString(reachabilityInfos: List<ReachabilityInfo>): String {
+    return transformToStringBy(reachabilityInfos, "\n") { sourceFqn, targetFqn, description, isTargetContagious ->
+        val comment = description + (if (isTargetContagious) "[CONTAGIOUS!]" else "")
+        val info = "\"$sourceFqn\" -> \"$targetFqn\"" + (if (comment.isBlank()) "" else " // $comment")
+
+        info
+    }
+}
+
+private fun transformToJsonString(reachabilityInfos: List<ReachabilityInfo>): String {
+    return "[\n" + transformToStringBy(reachabilityInfos, ",\n") { sourceFqn, targetFqn, description, isTargetContagious ->
+        """
+        |    {
+        |        "source" : "$sourceFqn",
+        |        "target" : "$targetFqn",
+        |        "description" : "$description",
+        |        "isTargetContagious" : $isTargetContagious
+        |    }""".trimMargin()
+    } + "\n]"
+}
+
+private fun transformToJsConstDeclaration(reachabilityInfos: List<ReachabilityInfo>): String {
+    return "const kotlinReachabilityInfos = " + transformToJsonString(reachabilityInfos) + ";"
+}

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/dce/Dce.kt

@@ -20,9 +20,14 @@ fun eliminateDeadDeclarations(modules: List<IrModuleFragment>, context: WasmBack
         context.configuration.getBoolean(JSConfigurationKeys.PRINT_REACHABILITY_INFO) ||
                 java.lang.Boolean.getBoolean("kotlin.wasm.dce.print.reachability.info")
 
+    val dumpReachabilityInfoToFile: String? =
+        context.configuration.get(JSConfigurationKeys.DUMP_REACHABILITY_INFO_TO_FILE)
+            ?: System.getProperty("kotlin.wasm.dce.dump.reachability.info.to.file")
+
     val usefulDeclarations = WasmUsefulDeclarationProcessor(
         context = context,
-        printReachabilityInfo = printReachabilityInfo
+        printReachabilityInfo = printReachabilityInfo,
+        dumpReachabilityInfoToFile
     ).collectDeclarations(rootDeclarations = buildRoots(modules, context))
 
     val remover = WasmUselessDeclarationsRemover(usefulDeclarations)

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/dce/WasmUsefulDeclarationProcessor.kt

@@ -18,8 +18,9 @@ import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstanceOrNull
 
 internal class WasmUsefulDeclarationProcessor(
     override val context: WasmBackendContext,
-    printReachabilityInfo: Boolean
+    printReachabilityInfo: Boolean,
-) : UsefulDeclarationProcessor(printReachabilityInfo, removeUnusedAssociatedObjects = false) {
+    dumpReachabilityInfoToFile: String?
+) : UsefulDeclarationProcessor(printReachabilityInfo, removeUnusedAssociatedObjects = false, dumpReachabilityInfoToFile) {
 
     private val unitGetInstance: IrSimpleFunction = context.findUnitGetInstanceFunction()
 

js/js.frontend/src/org/jetbrains/kotlin/js/config/JSConfigurationKeys.java

@@ -94,6 +94,9 @@ public class JSConfigurationKeys {
     public static final CompilerConfigurationKey<Boolean> PRINT_REACHABILITY_INFO =
             CompilerConfigurationKey.create("print declarations' reachability info during performing DCE");
 
+    public static final CompilerConfigurationKey<String> DUMP_REACHABILITY_INFO_TO_FILE =
+            CompilerConfigurationKey.create("dump declarations' reachability info to file during performing DCE");
+
     public static final CompilerConfigurationKey<Boolean> FAKE_OVERRIDE_VALIDATOR =
             CompilerConfigurationKey.create("IR fake override validator");