Direct instantiations of VirtualFileKotlinClass are replaced by access to caching service

compiler/cli/src/org/jetbrains/jet/cli/jvm/compiler/CliVirtualFileFinder.java

@@ -46,7 +46,7 @@ public class CliVirtualFileFinder extends VirtualFileKotlinClassFinder implement
 
     //NOTE: copied with some changes from CoreJavaFileManager
     @Nullable
-    private static VirtualFile findFileInRoot(@NotNull String qName, @NotNull VirtualFile root) {
+    private VirtualFile findFileInRoot(@NotNull String qName, @NotNull VirtualFile root) {
         String pathRest = qName;
         VirtualFile cur = root;
 
@@ -70,7 +70,7 @@ public class CliVirtualFileFinder extends VirtualFileKotlinClassFinder implement
                 return null;
             }
             //NOTE: currently we use VirtualFileFinder to find Kotlin binaries only
-            if (KotlinClassHeader.read(new VirtualFileKotlinClass(vFile)) != null) {
+            if (KotlinClassHeader.read(createKotlinClass(vFile)) != null) {
                 return vFile;
             }
         }

compiler/frontend.java/src/org/jetbrains/jet/lang/resolve/kotlin/VirtualFileKotlinClassFinder.java

@@ -17,16 +17,34 @@
 package org.jetbrains.jet.lang.resolve.kotlin;
 
 import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.util.containers.SLRUCache;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.resolve.name.FqName;
 
 public abstract class VirtualFileKotlinClassFinder implements VirtualFileFinder {
 
+    // This cache must be small: we only query the same file a few times in a row (from different places)
+    private final SLRUCache<VirtualFile, KotlinJvmBinaryClass> cache = new SLRUCache<VirtualFile, KotlinJvmBinaryClass>(2, 2) {
+        @NotNull
+        @Override
+        public KotlinJvmBinaryClass createValue(VirtualFile virtualFile) {
+            return new VirtualFileKotlinClass(virtualFile);
+        }
+    };
+
     @Nullable
     @Override
     public KotlinJvmBinaryClass findKotlinClass(@NotNull FqName fqName) {
         VirtualFile file = findVirtualFile(fqName);
-        return file == null ? null : new VirtualFileKotlinClass(file);
+        return file == null ? null : createKotlinClass(file);
+    }
+
+    @Override
+    @NotNull
+    public KotlinJvmBinaryClass createKotlinClass(@NotNull VirtualFile file) {
+        synchronized (cache) {
+            return cache.get(file);
+        }
     }
 }