From 917930ba5364e27f81ef447d5fa35ab642b3abfd Mon Sep 17 00:00:00 2001
From: Nikolay Igotti <olonho@users.noreply.github.com>
Date: Wed, 7 Feb 2018 10:52:51 +0300
Subject: [PATCH] Make empty array handling more efficient, also fixes KT-21758
 (#1285)

* Make empty array handling more efficient, also fixes KT-21758

* Fix WebAssembly.
---
 runtime/src/main/cpp/Arrays.cpp          | 12 ++++++++++++
 runtime/src/main/cpp/Types.h             |  1 -
 runtime/src/main/kotlin/kotlin/Arrays.kt |  6 ++----
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/runtime/src/main/cpp/Arrays.cpp b/runtime/src/main/cpp/Arrays.cpp
index 4b5dc271176..f344e9b7cfd 100644
--- a/runtime/src/main/cpp/Arrays.cpp
+++ b/runtime/src/main/cpp/Arrays.cpp
@@ -39,6 +39,14 @@ static inline void copyImpl(KConstRef thiz, KInt fromIndex,
           count * sizeof(T));
 }
 
+namespace {
+
+const ArrayHeader anEmptyArray = {
+  theArrayTypeInfo, /* permanent object */ 0, /* element count */ 0
+};
+
+}  // namespace
+
 extern "C" {
 
 // TODO: those must be compiler intrinsics afterwards.
@@ -98,6 +106,10 @@ void Kotlin_Array_copyImpl(KConstRef thiz, KInt fromIndex,
 }
 
 // Arrays.kt
+OBJ_GETTER0(Kotlin_emptyArray) {
+  RETURN_OBJ(const_cast<ObjHeader*>(anEmptyArray.obj()));
+}
+
 KByte Kotlin_ByteArray_get(KConstRef thiz, KInt index) {
   const ArrayHeader* array = thiz->array();
   if (static_cast<uint32_t>(index) >= array->count_) {
diff --git a/runtime/src/main/cpp/Types.h b/runtime/src/main/cpp/Types.h
index 2219cc818b4..33338e71065 100644
--- a/runtime/src/main/cpp/Types.h
+++ b/runtime/src/main/cpp/Types.h
@@ -71,7 +71,6 @@ extern "C" {
 #endif
 
 extern const TypeInfo* theAnyTypeInfo;
-extern const TypeInfo* theCloneableTypeInfo;
 extern const TypeInfo* theArrayTypeInfo;
 extern const TypeInfo* theByteArrayTypeInfo;
 extern const TypeInfo* theCharArrayTypeInfo;
diff --git a/runtime/src/main/kotlin/kotlin/Arrays.kt b/runtime/src/main/kotlin/kotlin/Arrays.kt
index ec785784b3f..168705f9c80 100644
--- a/runtime/src/main/kotlin/kotlin/Arrays.kt
+++ b/runtime/src/main/kotlin/kotlin/Arrays.kt
@@ -12667,10 +12667,8 @@ public inline fun <reified T> Collection<T>.toTypedArray(): Array<T> {
 @Suppress("UNCHECKED_CAST")
 public inline fun <reified @PureReifiable T> arrayOf(vararg elements: T): Array<T> = elements as Array<T>
 
-private val kEmptyArray = arrayOf<Any>()
-
-@Suppress("UNCHECKED_CAST")
-public fun <T> emptyArray() = kEmptyArray as Array<T>
+@SymbolName("Kotlin_emptyArray")
+external public fun <T> emptyArray(): Array<T>
 
 /**
  * Returns an array containing the specified [Double] numbers.