Improve performance of $kotlinClass field initializer

Don't load annotations reflectively in each class' <clinit>

compiler/backend/src/org/jetbrains/jet/codegen/ImplementationBodyCodegen.java

@@ -475,7 +475,7 @@ public class ImplementationBodyCodegen extends ClassBodyCodegen {
             return;
         }
 
-        generateReflectionObjectField(state, classAsmType, v, method("kClass", K_CLASS_IMPL_TYPE, getType(Class.class)),
+        generateReflectionObjectField(state, classAsmType, v, method("kClassFromKotlin", K_CLASS_IMPL_TYPE, getType(Class.class)),
                                       JvmAbi.KOTLIN_CLASS_FIELD_NAME, createOrGetClInitCodegen().v);
     }
 

core/runtime.jvm/src/kotlin/reflect/jvm/internal/KClassImpl.kt

@@ -29,11 +29,13 @@ enum class KClassOrigin {
 private val KOTLIN_CLASS_ANNOTATION_CLASS = javaClass<KotlinClass>()
 private val KOTLIN_SYNTHETIC_CLASS_ANNOTATION_CLASS = javaClass<KotlinSyntheticClass>()
 
-class KClassImpl<out T>(val jClass: Class<T>) : KClass<T> {
+class KClassImpl<out T>(val jClass: Class<T>, isKnownToBeKotlin: Boolean) : KClass<T> {
     // TODO: write metadata to local classes
-    val origin: KClassOrigin =
-            if (jClass.isAnnotationPresent(KOTLIN_CLASS_ANNOTATION_CLASS) ||
-                jClass.isAnnotationPresent(KOTLIN_SYNTHETIC_CLASS_ANNOTATION_CLASS)) {
+    private val origin: KClassOrigin =
+            if (isKnownToBeKotlin ||
+                jClass.isAnnotationPresent(KOTLIN_CLASS_ANNOTATION_CLASS) ||
+                jClass.isAnnotationPresent(KOTLIN_SYNTHETIC_CLASS_ANNOTATION_CLASS)
+            ) {
                 KClassOrigin.KOTLIN
             }
             else {

core/runtime.jvm/src/kotlin/reflect/jvm/internal/factory.kt

@@ -19,7 +19,10 @@ package kotlin.reflect.jvm.internal
 import kotlin.reflect.*
 
 fun <T> kClass(jClass: Class<T>): KClassImpl<T> =
-        KClassImpl<T>(jClass)
+        KClassImpl<T>(jClass, false)
+
+fun <T> kClassFromKotlin(jClass: Class<T>): KClassImpl<T> =
+        KClassImpl<T>(jClass, true)
 
 fun kPackage(jClass: Class<*>): KPackageImpl =
         KPackageImpl(jClass)

core/runtime.jvm/src/kotlin/reflect/jvm/internal/foreignKClasses.kt

@@ -53,13 +53,13 @@ fun <T> foreignKotlinClass(jClass: Class<T>): KClassImpl<T> {
         val newArray = arrayOfNulls<WeakReference<KClassImpl<*>>>(size + 1)
         // Don't use Arrays.copyOf because it works reflectively
         System.arraycopy(cached, 0, newArray, 0, size)
-        val newKClass = KClassImpl<T>(jClass)
+        val newKClass = kClass<T>(jClass)
         newArray[size] = WeakReference(newKClass)
         FOREIGN_K_CLASSES = FOREIGN_K_CLASSES.plus(name, newArray)
         return newKClass
     }
 
-    val newKClass = KClassImpl<T>(jClass)
+    val newKClass = kClass<T>(jClass)
     FOREIGN_K_CLASSES = FOREIGN_K_CLASSES.plus(name, WeakReference(newKClass))
     return newKClass
 }