JS DCE: inline Qualifier class to reduce RAM usage

js/js.dce/src/org/jetbrains/kotlin/js/dce/Analyzer.kt

@@ -278,7 +278,7 @@ class Analyzer(private val context: Context) : JsVisitor() {
                     leftNode.addFunction(rhs)
                     return leftNode
                 }
-                leftNode.qualifier?.memberName == Namer.METADATA -> {
+                leftNode.memberName == Namer.METADATA -> {
                     // lhs.$metadata$ = expression
                     // During reachability tracking phase: eliminate it if lhs is unreachable, traverse expression
                     // It's commonly used to supply class's metadata

js/js.dce/src/org/jetbrains/kotlin/js/dce/Context.kt

@@ -76,7 +76,7 @@ class Context {
 
     fun extractNode(expression: JsExpression): Node? {
         val node = extractNodeImpl(expression)?.original
-        return if (node != null && moduleExportsNode in generateSequence(node) { it.qualifier?.parent }) {
+        return if (node != null && moduleExportsNode in generateSequence(node) { it.parent }) {
             val path = node.pathFromRoot().drop(2)
             path.fold(currentModule.original) { n, memberName -> n.member(memberName) }
         }
@@ -134,7 +134,7 @@ class Context {
 
     fun visit(n: Node) = n.visit(currentColor)
 
-    class Node private constructor(val localName: JsName?, qualifier: Qualifier?) {
+    class Node private constructor(val localName: JsName?, parent: Node?, val memberName: String?) {
         private var _dependenciesImpl: MutableSet<Node>? = null
         private var _expressionsImpl: MutableSet<JsExpression>? = null
         private var _functionsImpl: MutableSet<JsFunction>? = null
@@ -183,7 +183,7 @@ class Context {
                 original.declarationReachableImpl = value
             }
 
-        var qualifier: Qualifier? = qualifier
+        var parent: Node? = parent
             private set
 
         private var color: Byte = 0
@@ -196,7 +196,7 @@ class Context {
 
         val memberNames: Set<String> get() = original._membersImpl?.keys ?: emptySet()
 
-        constructor(localName: JsName? = null) : this(localName, null)
+        constructor(localName: JsName? = null) : this(localName, null, null)
 
         var original: Node = this
             get() {
@@ -225,20 +225,20 @@ class Context {
             original.usedByAstNodesImpl += node
         }
 
-        fun member(name: String): Node = original.membersImpl.getOrPut(name) { Node(null, Qualifier(this, name)) }.original
+        fun member(name: String): Node = original.membersImpl.getOrPut(name) { Node(null, this, name) }.original
 
         fun alias(other: Node) {
             val a = original
             val b = other.original
             if (a == b) return
 
-            if (a.qualifier == null && b.qualifier == null) {
+            if (a.parent == null && b.parent == null) {
                 a.merge(b)
             }
-            else if (a.qualifier == null) {
+            else if (a.parent == null) {
                 if (b.root() == a) a.makeDependencies(b) else b.evacuateFrom(a)
             }
-            else if (b.qualifier == null) {
+            else if (b.parent == null) {
                 if (a.root() == b) a.makeDependencies(b) else a.evacuateFrom(b)
             }
             else {
@@ -257,12 +257,12 @@ class Context {
 
             for ((name, member) in newMembers) {
                 membersImpl[name] = member
-                member.original.qualifier = Qualifier(this, member.original.qualifier!!.memberName)
+                member.original.parent = this
             }
             for ((name, member) in existingMembers) {
                 membersImpl[name]!!.original.merge(member.original)
                 membersImpl[name] = member.original
-                member.original.qualifier = Qualifier(this, member.original.qualifier!!.memberName)
+                member.original.parent = this
             }
             other.membersImpl.clear()
 
@@ -301,14 +301,12 @@ class Context {
             }
         }
 
-        fun root(): Node = generateSequence(original) { it.qualifier?.parent?.original }.last()
+        fun root(): Node = generateSequence(original) { it.parent?.original }.last()
 
         fun pathFromRoot(): List<String> =
-                generateSequence(original) { it.qualifier?.parent?.original }.mapNotNull { it.qualifier?.memberName }
+                generateSequence(original) { it.parent?.original }.mapNotNull { it.memberName }
                         .toList().asReversed()
 
         override fun toString(): String = (root().localName?.ident ?: "<unknown>") + pathFromRoot().joinToString("") { ".$it" }
     }
-
+}
-    class Qualifier(val parent: Node, val memberName: String)
-}

js/js.dce/src/org/jetbrains/kotlin/js/dce/ReachabilityTracker.kt

@@ -102,8 +102,8 @@ class ReachabilityTracker(
             invocation in analysisResult.invocationsToSkip -> {}
             else -> {
                 val node = context.extractNode(invocation.qualifier)
-                if (node != null && node.qualifier?.memberName in CALL_FUNCTIONS) {
+                if (node != null && node.memberName in CALL_FUNCTIONS) {
-                    val parent = node.qualifier!!.parent
+                    val parent = node.parent!!
                     reach(parent)
                     currentNodeWithLocation?.let { parent.addUsedByAstNode(it) }
                 }
@@ -178,15 +178,14 @@ class ReachabilityTracker(
         var current = node
         while (true) {
             for (ancestorDependency in current.dependencies) {
-                if (current in generateSequence(ancestorDependency) { it.qualifier?.parent }) continue
+                if (current in generateSequence(ancestorDependency) { it.parent }) continue
                 val dependency = path.asReversed().fold(ancestorDependency) { n, memberName -> n.member(memberName) }
                 if (!dependency.reachable) {
                     reportAndNest("reach: dependency $dependency", null) { reach(dependency) }
                 }
             }
-            val qualifier = current.qualifier ?: break
+            path += current.memberName ?: break
-            path += qualifier.memberName
+            current = current.parent!! // memberName != null => parent != null
-            current = qualifier.parent
         }
     }
 
@@ -202,7 +201,7 @@ class ReachabilityTracker(
                 reachableNodesImpl += node
             }
 
-            node.original.qualifier?.parent?.let {
+            node.original.parent?.let {
                 reportAndNest("reach-decl: parent $it", null) {
                     reachDeclaration(it)
                 }

js/js.dce/src/org/jetbrains/kotlin/js/dce/printTree.kt

@@ -24,7 +24,7 @@ fun printTree(root: Node, consumer: (String) -> Unit, printNestedMembers: Boolea
 
 private fun printTree(node: Node, consumer: (String) -> Unit, depth: Int, settings: Settings) {
     val sb = StringBuilder()
-    sb.append("  ".repeat(depth)).append(node.qualifier?.memberName ?: node.toString())
+    sb.append("  ".repeat(depth)).append(node.memberName ?: node.toString())
 
     if (node.reachable) {
         sb.append(" (reachable")

js/js.dce/src/org/jetbrains/kotlin/js/dce/util.kt

@@ -83,11 +83,11 @@ fun Iterable<Node>.extractReachableRoots(context: Context): Iterable<Node> {
 
 private fun Node.extractRootsImpl(target: MutableList<Node>, context: Context) {
     if (!context.visit(original)) return
-    val qualifier = original.qualifier
+    val parent = original.parent
-    if (qualifier == null) {
+    if (parent == null) {
         target += original
     }
     else {
-        qualifier.parent.extractRootsImpl(target, context)
+        parent.extractRootsImpl(target, context)
     }
 }