From 4b0b9e1f80a7d8cfd88216c64df9fa8c0cf67359 Mon Sep 17 00:00:00 2001
From: pyos <pyos@google.com>
Date: Thu, 25 Apr 2019 10:52:06 +0200
Subject: [PATCH] JVM_IR: make ToArrayLowering linear in complexity

by not running DFS from every node visited during another DFS.
---
 .../backend/jvm/lower/ToArrayLowering.kt      | 29 +++++++------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/ToArrayLowering.kt b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/ToArrayLowering.kt
index 7cde74df8c3..35264f7e229 100644
--- a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/ToArrayLowering.kt
+++ b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/ToArrayLowering.kt
@@ -39,19 +39,10 @@ internal val toArrayPhase = makeIrFilePhase(
 private class ToArrayLowering(private val context: JvmBackendContext) : ClassLoweringPass {
 
     override fun lower(irClass: IrClass) {
-        if (irClass.isJvmInterface) return
+        if (irClass.isJvmInterface || !irClass.isDirectCollectionSubClass()) return
 
         val irBuiltIns = context.irBuiltIns
 
-        if (!irClass.isCollectionSubClass()) return
-
-        if (irClass.hasSuperClass {
-                it != irClass &&
-                        it.isClass &&
-                        it.origin != IrDeclarationOrigin.IR_EXTERNAL_JAVA_DECLARATION_STUB &&
-                        it.isCollectionSubClass()
-            }) return
-
         val toArrayName = Name.identifier("toArray")
         val genericToArray = irClass.declarations.find { it.isGenericToArray() }
         val nonGenericToArray = irClass.declarations.find { it.isNonGenericToArray() }
@@ -305,15 +296,15 @@ private class ToArrayLowering(private val context: JvmBackendContext) : ClassLow
     }
 }
 
-private fun IrClass.hasSuperClass(pred: (IrClass) -> Boolean): Boolean =
-    DFS.ifAny(
-        listOf(this),
-        { irClass -> irClass.superTypes.mapNotNull { ((it as? IrSimpleType)?.classifier as? IrClassSymbol)?.owner } },
-        pred
-    )
+private val IrClass.superClasses
+    get() = superTypes.mapNotNull { it.getClass() }
 
 // Have to check by name, since irBuiltins is unreliable.
 private fun IrClass.isCollectionSubClass() =
-    hasSuperClass {
-        it.defaultType.isCollection()
-    }
\ No newline at end of file
+    DFS.ifAny(listOf(this), IrClass::superClasses) { it.defaultType.isCollection() }
+
+// If this class inherits from another Kotlin class that implements Collection, it already has toArray.
+private fun IrClass.isDirectCollectionSubClass() =
+    isCollectionSubClass() && !superClasses.any {
+        it.isClass && it.origin != IrDeclarationOrigin.IR_EXTERNAL_JAVA_DECLARATION_STUB && it.isCollectionSubClass()
+    }